The Doctor - Patrick Troughton
Jamie McCrimmon - Frazer Hines
Victoria Waterfield - Deborah Watling

Professor Edward Travers - Jack Watling
Colonel Lethbridge-Stewart - Nicholas Courtney
Anne Travers - Tina Packer
Julius Silverstein - Frederick Schrecker
Corporal Lane - Rod Beacham
Corporal Blake - Richardson Morgan
Captain Knight - Ralph Watson
Harold Chorley - Jon Rollason
Staff Sgt. Arnold - Jack Woolgar
Craftsman Weams - Stephen Whittaker
Soldier - Bernard G. High
Yeti - John Levene, John Lord, Gordon Stothard, Colin Warman, Jeremy King, Roger Jacombs
Soldier - Joseph O'Connell
Driver Evans - Derek Pollitt

Assistant Floor Manager - Roselyn Parker
Costumes - Martin Baugh
Designer - David Myerscough-Jones
Fight Arranger - Derek Ware
Film Cameramen - Alan Jonas, Jimmy Court
Film Editors - Philip Barnikel, Colin Hobson
Make-Up - Sylvia James
Producer - Peter Bryant
Production Assistant - Gareth Gwenlan
Script Editor - Derrick Sherwin
Special Sounds - Brian Hodgson
Studio Lighting - Clive Leighton
Studio Sound - Ray Angel
Theme Arrangement - Delia Derbyshire
Title Music - Ron Grainer
Visual Effects - Ron Oates

After being caught up in a web-like substance on its journey through space, the TARDIS arrives in the tunnels of the London Underground railway system, only to find the web also in the tunnels - as is the Great Intelligence's Yeti.

How has this happened? The team learn that the impending disaster was triggered nearly forty years before, after their previous encounter with the Intelligence. Professor Travers accidentally reactivated a Yeti, thus giving the Intelligence the ammunition it needed to plan another invasion attempt.

The aim is simple: the Intelligence wants to drain the Doctor's mind. Army forces, led by Colonel Lethbridge-Stewart, help the Doctor and his team race against time to stop them in their mission. Can they make it?

Episode One

The TARDIS continues in flight with the doors open, while the evil Salamander has been ejected into space and time. Jamie flings himself onto the console and activates the door control, nearly being sucked out himself.

Anne Travers meets with her agitated father, Professor Travers, who pleads with Silverstein to let him take (or buy) back the Yeti he sold to him thirty years ago. The Professor claims to have reactivated a control sphere, but it has disappeared. Anne suspects his senility is playing tricks on him. She takes her father away at Silverstein's urging. As Silverstein closes his museum for the night, the sphere breaks through a window and reconnects with the Yeti. As it metamorphoses into a glowing-eyed monster, Silverstein is attacked; he cowers in terror.

Jamie tries to convince the Doctor that a light on the console is flashing; the Doctor dismisses it. Victoria notices the light too and when the Doctor finally sees it for himself, the machine emits landing sounds. Strangely, the scanner reveals they are suspended in space and as they watch, the scanner picture (and the TARDIS itself) is enveloped by a web-like substance.

In an underground fortress, Captain Knight is being interviewed about an apparently fallen comrade, Colonel Pemberton, by Harold Chorley of London Television. As the interview concludes, Professor Travers is ushered in. Knight is badgered by the Professor. He explains that Anne asked for him to be brought in. When Knight leaves, the Professor begins badgering Chorley and when Chorley attempts to interview him about the "scientific section" and finding "a solution to the problem," Travers opines that the whole of London might be completely wiped out.

The Doctor has rigged up a device. He plugs it into the console. As the web lessens, he throws the switch on the device, the TARDIS lurches and the Doctor announces he has landed the ship near where they were expected, eluding their captors for the moment. The TARDIS has landed, they soon discover, at the entrance to the London Underground station at Covent Garden.

The crew arrive in Covent Garden The gate at the top of the stairs is closed. When Jamie attempts to rouse a sleeping man just outside, the man slumps dead, covered with web. The newsstand outside reads, "Londoners Flee! Menace Spreads!" Returning to the platform, Jamie hastily jumps onto the tracks. The Doctor quickly and thankfully ascertains that the current that would have electrocuted Jamie is off.

The three walk along the tracks into the tunnel, noticing that trains have not been running for some time. They discover a power cable and are forced to hide as three soldiers, Staff Sergeant Arnold, Corporal Blake and Craftsman Weams, appear, letting out more cable from a large spool. The Doctor asks his friends to follow the soldiers at a distance while he finds where the cables lead. As they do so, Victoria cannot stifle a scream as she walks right into some cobweb. The soldiers capture them.

The Doctor reaches the Charing Cross platform, on which several crates of explosives are connected to the cables. As he investigates, he hears a too-familiar bleeping sound. He ducks onto the tracks and hides under the platform, as a Yeti emerges.

Corporal Lane cannot raise communications with a truck at Holborn. Anne enters with a repaired blast recorder and Knight is only too pleased to give her a hand. Chorley enters, complaining of Professor Travers' obstructiveness, but is ushered out by Knight. Meanwhile, the Doctor must sit tight as a second Yeti arrives on the platform. Both Yeti cover the explosives in web, using a strange kind of gun.

As Knight continues to set his cap at Anne Travers, Arnold returns with the cables ready to connect for the demolition job. Arnold reports the two captured youngsters and Anne pushes to make sure there's no one else in the tunnel before it's blown up. Arnold questions them and Jamie makes a snap decision to deny they were with anyone else. With the Yeti gone, the Doctor closely examines the web-covered crates. The bombs are detonated: the web glows and flashes underneath as the Doctor is thrown from the platform.

Episode Two

Jamie and Victoria wait in their makeshift prison (the common room at the fortress) while Arnold reports to Knight about the Doctor. Arnold is dispatched to investigate as Weams reports that the blast recorder that Anne repaired isn't working: it hasn't recorded a blast. Weams suggests sabotage by the Doctor, and Knight goes to interrogate the youngsters further.

As Knight, Anne, and Chorley question Jamie and Victoria, Jamie in turn tries to get someone to tell them where they are and what's going on. Weams interrupts to report contact is reestablished with Holborn, but it sounds like they're in trouble. When Knight asks if it's Yeti and he leaves with Weams, Jamie and Victoria wonder if they heard him right. Lane reports firing heard at Holborn, they overhear what sounds like a Yeti attack and the line goes dead. Knight collects some soldiers and goes out to investigate; Chorley elects to stay behind.

Arnold and Corporal Blake discover at Charing Cross the explosives' shattered crates covered in web.

With no sign of the Doctor, they note the distinct lack of any blast damage. Back at the fortress, Travers is working on a control sphere when Anne tells him of the new arrivals who know so much about the Yeti. Jamie and Victoria suspect it must have been the Great Intelligence that attempted to capture them in space. Travers bursts in and questions them, but Victoria recognises their 31-years-older friend they met in Tibet in 1935. Travers takes Jamie to find out any news about the Doctor, while Victoria is left to explain to Anne how all this is possible.

Arnold tells Jamie and Travers what he knows and his suspicions about the Doctor. Jamie goads Arnold into taking him out in search of the Doctor. As Victoria continues to explain, Chorley enters and sits at his typewriter to work on a story about the Doctor. Anne regards him with contempt, calling him a "sensation-monger" working for the "gutter press." Chorley presses Victoria for more information, and tells her that Jamie has gone back into the tunnels.

On the way back from Holborn, Knight and Private Thompson construct a barricade across the tunnel from explosives recovered from the dead ammo detail. Lane and Privates O'Brien and Cocksey perform a rear-guard action but are attacked by Yeti. As they gradually retreat towards the barricade Cocksey loses his footing and is beaten to death by a Yeti.
O'Brien's rifle jamsO'Brien's rifle jams and he is smothered in web, which kills him. Arnold and Jamie meet Thompson, Knight and Lane. As Knight shoots the barricade to blow up the tunnel, the blast is contained because the Yeti cocoon it in web. They are trapped by Yeti from the other end of the tunnel and are held prisoner.

Anne discusses with her father the curious fact that every time he's met the Yeti, he's met the Doctor. Before he can refute this assertion, Victoria returns (having overheard) with tea. She quickly excuses herself, after which Anne is convinced the Doctor is not behind this menace. Out in the tunnels, Jamie, Knight, Arnold, Lane, and Thompson are under guard by motionless Yeti. Suddenly their guards are called away by a bleeping signal, leaving the humans puzzled, but free.

Blake and Weams, via an illuminated map in the Ops Room, see that the web-fungus is advancing through the tunnels for the first time in three weeks. They bring Travers, Anne, and Chorley to see, and Chorley suspects Jamie and Victoria are spies for the Doctor. Blake notices that there's no sign of Victoria in the fortress. She is out searching for her friends in the tunnels.

As Jamie, Arnold, Knight, and company return through the tunnels, they hear someone approaching; oddly, the man is singing in Welsh. He is Evans, the driver of the ammunition truck to Holborn. He reports seeing the web advancing, and a Yeti carrying a glass-like pyramid at King's Cross station. Jamie excitedly tells the men that if they destroyed that, it would knock out the Intelligence, and he insists on going there and continuing the search for the Doctor. Evans volunteers to go with him as the rest of the men return to the fortress, but as Jamie thanks Evans thanks, Evans assures him that he'll escape the first chance he gets. The web continues to advance along the Circle Line, as Evans and Jamie arrive at Cannon Street, heading on the Circle Line towards the Monument.

Knight and his party arrive at the fortress and are brought up to date. Chorley is pressing for escape but Knight shuts him down. Victoria is still searching the tunnels as a figure ducks into the shadows as she passes. The Circle Line is completely inundated except for the Monument. Arriving there, Jamie and Evans see the web advancing from both directions; they are trapped.

Episode Three

Out of the web advances a Yeti carrying a pyramid. Jamie gets Evans to shoot the pyramid, causing the Yeti to become immobile, but the web continues to advance. They make a dash for an archway, and escape.

Meanwhile, Victoria finds the Doctor in the tunnels, accompanied by a Colonel Lethbridge-Stewart. She tells the Colonel about the fortress at Goodge Street, and at his prompting, tells the Doctor about the presence of Travers, and his apparent suspicions about the Doctor. The Colonel escorts them to the fortress.

With the Circle Line completely cut off and the fortress hemmed in, Knight is informed of the return of the Doctor and Victoria, and the arrival of the Colonel. In the common room, the Colonel presents his papers of authorisation and tells Knight that he is Colonel Pemberton's replacement. The Colonel was part of the attacked ammunition party at Holborn, and Knight mentions to him that driver Evans survived also, still not quite certain if his new C.O. is the real thing. Travers bursts in and, after a happy reunion, takes the Doctor and Victoria to the lab, where the Doctor ensures suspicions are not focused on him. As they muse about the Great Intelligence and its reasons for trapping the TARDIS, Victoria worries about Jamie.

Jamie and Evans arrive at St. Paul's station. Meanwhile, Chorley is arguing with Arnold about trying to escape, saying his reports to the outside world are important. Arnold dismisses any thought of getting through the web. In the lab, Travers tells the Doctor about reactivating a control sphere. Knight collects them all for a briefing to be given in the common room for the Colonel's benefit.

Evans plans to escape at Chancery Lane, hoping to find his lorry and get out of town. Jamie argues with him as they walk through the tunnels, but Evans separates from him.

The TARDIS crew find out about the mistAt the briefing, they discuss the arrival of the web-mist in London, how anyone going inside this mist never comes out again, and its complete interference with radio and other communications. The Doctor and Travers note the new appearance of the Yeti. Anne reports that she and her father believe they could jam transmissions from the Intelligence, but need more equipment. Chorley bursts in, clearly agitated that he was not told about this briefing, and argues that an exit to the surface, mentioned by Arnold, could allow a helicopter to airlift them out. The Colonel dismisses him and his attempts to pull rank as a member of the press. Chorley leaves to question Weams in the Ops Room about tall buildings in this area, which include the Post Office Tower. Weams in turn leaves to tell the Colonel about another advance of the web-fungus.

Jamie surprises Evans in the tunnels, and learns that Evans' plan to escape has failed, so they make their way back to the fortress. The Colonel decides to give Chorley a liaison job, coordinating things (and tucked out of the way in the common room), while the rest get to some real work. The Doctor suggests buying some time by blowing up the tunnel at Goodge Street, sealing themselves in, using explosives on a baggage trolley as it rolls down the tracks, so avoiding any Yeti attempts to cocoon it. The Doctor and Travers set to work on a detonator. Meanwhile, someone in the fortress unlocks the main door, leaving the base open and vulnerable.

In the lab, Victoria recognises the model Yeti that Anne shows her (as she saw in Tibet), but as the Doctor comes in, Anne realises that one of them is missing. It is in the hands of the traitor, who places the homing device at the doorway of the explosives store; in response, a Yeti in the tunnels moves towards the fortress. Victoria points out that Jamie will be trapped outside the fortress if their plan succeeds, but it soon becomes moot: the Yeti does its job, and soon the base crew discover the explosives shrouded in web.

The Colonel decides to take a group of men to Holborn to see if any explosives are still usable; both the Doctor and the Colonel suspect this is a waste of time but they must check. The Doctor announces that someone inside the base is in league with the Yeti, citing the evidence of this latest precision attack. Victoria foolishly tells Chorley about the TARDIS and the plans to blow up the tunnel, and as the Doctor arrives, Chorley leaves surreptitiously. The Doctor soon discovers her gaffe, and also discovers they are locked in the common room. Chorley meets Jamie and Evans, safely arrived at the fortress, and they tell him the Colonel's party has gone to Holborn; he leaves the base. Jamie releases the Doctor and Victoria, and they leave in pursuit of Chorley.

As Travers and Anne work in the lab, a scream is heard. Travers soon finds Weams dead in the Ops Room. He is covered in web, a model Yeti lying beside him, and as Travers picks it up, a Yeti roars behind him and attacks.

Episode Four

Anne appears, and just as she sees her father on the ground, she too is struck down. The Yeti drag away the Professor. The Doctor, Jamie, Victoria, and Evans are en route to Convent Garden, trying to intercept Chorley, who the Doctor suspects will attempt to use the TARDIS to escape from the Underground. The Colonel and Arnold meet up with Knight, who reports running into web-fungus a mere 100 yards from Holborn. Arnold notes that it was as if the Intelligence knew what they were up to. Knight suggests attempting another route, via Piccadilly, and the Colonel leads the party there.

The Doctor and his party run into more web-fungus before reaching Covent Garden, but he cannot be sure if Chorley made it to the TARDIS. He collects a sample of the web in Evans' tobacco tin (casually discarding the tobacco inside, to Evans' irritation), even as the web reacts violently. Arnold and Blake are investigating a tunnel, and just after Blake's return to the main party, the Doctor and party find Arnold. Arnold then reports back to the Colonel as the rest return to the fortress.

The Doctor and company discover the main door hanging off its hinges, and soon discover web-covered furniture, equipment—and bodies. They discover Anne in the lab and rouse her from unconsciousness. She is soon hysterical as she tells of her father's fate, and Jamie and Victoria help her to the common room. The Doctor tells the Colonel and Knight upon their return about what has happened, including Chorley's activities. Evans is drafted by Arnold to help with the bodies, and on his exit greets the Colonel, whose memory is refreshed about the lorry driver to Holborn.

The Doctor and the Colonel are summoned by Blake to the Ops Room, where more stations are being overtaken by web-fungus as it advances towards Goodge Street.

The Doctor explains about the Great Intelligence and the TARDISThe Colonel muses about the Doctor's suggestion of a traitor in their midst, and the Doctor tries to explain what exactly the Great Intelligence is, that he and his friends are time-travellers, and that their police-box-shaped craft is at Covent Garden. Jamie enters to take the Doctor to Anne, who is asking for him. Despite Knight's strong doubts, the Colonel decides to try to rescue the Doctor's craft.

Anne tells the Doctor that Travers was about to connect a controlling unit to the Sphere, and the Doctor now understands the reason why Travers was taken by the Intelligence. Anne shows the Doctor their work, saying that it won't override the Intelligence's commands, but the Doctor says they can fix that. Evans enters, giving the Doctor the model Yeti found by Weams' body, as per Arnold's instructions. The Doctor is horrified to be given it, and Evans denies any wrongdoing, as Anne realises all the other models are gone. Evans indignantly hands over his tobacco tin filled with web, as the Doctor and Anne deactivate the homing device inside the model.

The Colonel's plan gets underway: he and his party will attempt to reach Covent Garden station on the ground, while Arnold, Lane, and Evans will attempt to meet them underground via a trolley, using it to carry the TARDIS back to the fortress; Knight is ordered to remain on duty at the fortress. Meanwhile, the Doctor attempts to observe the web-fungus in the tin, but the tin is empty; the Doctor's suspicion of Evans grows. He, with Anne's help, persuades Knight to accompany them to the surface to obtain vital equipment needed to upgrade the controlling unit that is to be attached to the control sphere.

Arnold's party comes up against a web-fungus barrier near Covent Garden, and Arnold drafts Lane to attempt to get through the web on the trolley with him, the two wearing gas-masks. Evans pays out a rope attached as they go, but the two men scream as they enter, the web pulsating with light. Evans fearfully pulls at the rope, and the trolley emerges, with Lane's web-covered body sprawled out on it. Arnold is gone; Evans legs it.

On street-level, the Colonel and his men arrive at Covent Garden, but find Yeti waiting for them. After ducking into a builder's yard the Yeti find another way in, and the men open fire to no effect. The Yeti also smash down the main gate and force the men across the yard, killing some soldiers as they advance. Three men trapped behind a trader's cart are pinned down and killed by web guns. The bazooka is useless and another soldier is killed before the remaining troops retreat into a warehouse.

Knight sees the Doctor to a nearby electrical shop, but as they collect their supplies, two Yeti appear in the doorway, felling Knight. The Doctor finds a model Yeti in Knight's pocket. In the warehouse, Corporal Blake is killed. The Colonel, the only survivor, runs back to the fortress.

The Doctor dismantles the model Yeti as he and Anne start work with their new equipment. Victoria and Jamie are discussing who the traitor might be (Jamie suspects Chorley), when the Colonel staggers in and tells them of the fate of his men. Suddenly the Doctor shushes the room when he registers a faint bleeping sound. He realises someone in the room has the last model Yeti planted on them. They find it, but it's too late: two Yeti arrive, accompanied by a possessed Professor Travers.

Episode Five

The Great Intelligence speaks through the possessed Travers, saying the trap laid for the Doctor was so that it could possess him and his unsurpassed mind. It has created a machine that will drain all past knowledge from the Doctor's mind, leaving his body unharmed and his mind wiped clean, but he must submit willingly. To ensure his submission, Travers takes Victoria hostage and leaves, giving the Doctor twenty minutes to decide. A Yeti remains outside the lab door, so Jamie cannot go after Victoria, but the Doctor persuades everyone that the Intelligence cannot harm her or Travers if it is to obtain the Doctor's cooperation. Evans asks the Colonel why they don't just give the Doctor over to the Intelligence, so they can all go home. Travers and the Yeti take Victoria through the tunnels. As the Doctor, the Colonel, Jamie and Anne discuss their options, Evans discovers that a Yeti is no longer guarding them. The Colonel takes Evans and Jamie to search the base, while Anne and the Doctor work again on the control sphere and box, soon having a breakthrough. Jamie convinces the Colonel to go with him after the Yeti, while Evans gratefully stays behind on guard. They find web-fungus completely surrounding them through the door to the surface, and as it creeps in and forces the door open, the two retreat behind a fire door. Meanwhile, the Doctor has reactivated a control sphere as Jamie returns to them, telling them of their situation. The Colonel and Jamie are dubious about the merits of the Doctor and Anne's work, but are persuaded to leave them alone as they return to work on the control box.

Evans confronts the two men, claiming they must be working for the Intelligence: it did say it had another pair of hands working for it. Jamie dismisses his accusation, claiming it must have been Chorley. The Colonel and Jamie try their luck in the tunnels. At Piccadilly Circus Station, the Intelligence speaks through the air, orders Travers to release Victoria, and then releases him from possession. As Travers recovers his wits, they try to escape from the Yeti on the platform, only to run into another Yeti.

The Doctor and Anne successfully use the box to control the sphere, but only at short range; they set to work on reprogramming the sphere itself.

The Colonel and Jamie, now suspicious of each other, discover Victoria's handkerchief on the tracks in the tunnel and continue after her. At Piccadilly, now guarded by two Yeti, Staff Sgt. Arnold appears and, avoiding sight of the Yeti, tells Travers and Victoria he will try to get back to base. Evans is startled by the appearance of a control sphere at his feet, but the Doctor stops him before he tries to shoot it; it is now under the Doctor's control. The Doctor and Anne leave for the tunnels, heading towards Warren Street to try to find a Yeti to put their control sphere in. The Colonel and Jamie meet up with a shaken Arnold and take him back to the base. At a signal, the Yeti shepherd their prisoners along the platform.

Evans is hiding behind a board, after hearing something approaching, when the Colonel, Jamie, and Arnold enter. Evans is shocked and speechless at seeing Arnold again. When Evans explains where the Doctor and Anne have gone, Arnold sees the tracking signal of the fungus is heading towards Warren Street; the Colonel and Jamie go out after the scientists. The Doctor and Anne encounter a wall of fungus, and as they examine it they discover a Yeti is behind them! The Doctor hastily gets out the control box and — at dangerously close range — the Yeti freezes. They quickly replace its control sphere with theirs, and soon the Yeti is obeying the Doctor's commands.

Evans has dressed Arnold's head-wound, but as Evans returns the medical gear to the lab, he yells out in fear to Arnold: the wall of the laboratory is bulging, and it soon gives way as web-fungus spills into the room.

Episode Six

HQ is engulfed by the fungusArnold and Evans abandon the base as it is engulfed by web-fungus. Arnold wants to warn the others, but Evans deserts him and Arnold angrily shouts after him. The Doctor and Anne, in the tunnels with their controlled Yeti, decide not to tell anyone else about their success. The Doctor orders the Yeti to wait for them to leave, then resume acting for the Intelligence until he says otherwise. The Yeti obeys, and they leave. Jamie and the Colonel meet up with the Doctor and Anne, who are surprised to hear that Travers and Victoria are at Piccadilly, and that Arnold (who is still alive) told them so. The Doctor's Yeti reactivates after ninety seconds, and is soon joined by two more Yeti who move off together into the tunnels. Arnold is soon found by the party, and he tells his C.O. that the H.Q. has been swamped by web. No sooner are they all together than they are surrounded by the three Yeti. In another tunnel, two more Yeti find and capture Evans.

Arnold asks the Colonel to create a distraction, and he escapes from the Yeti. Travers and Victoria are led into the Booking Hall at Piccadilly Station, where they discover a strange apparatus with a throne-like seat linked to a pyramid. Victoria spots a figure lurking in the shadows, but it runs off before they can see who it is. As they discuss the Doctor's future, the Intelligence speaks to them through the air, insisting on their cooperation and non-interference. Travers wrings his hands at having brought this onto the world thanks to his curiosity.

As the main party is guarded on the Piccadilly platform, the Doctor explains to Jamie about the controlled Yeti. He gives Jamie a microphone to use to call the controlled Yeti to him—hopefully it will be the right one—and Jamie sneaks away. A frightened Harold Chorley finds Arnold and tells him his stories of the surface, the Yeti, fear... and the strange machine at Piccadilly station, including the Yeti and their two prisoners. Arnold wonders how he could possibly have survived all this time, and tells Chorley to come with him.

The Doctor tells Anne there's no point in trying to escape now; he must meet the Intelligence face to face. The Colonel asks the Doctor if he's going to give himself up, for the good of everyone, including his friends. Before he answers, Evans is brought in. Two Yeti start to move the Doctor away towards the Booking Hall, and he insists that they don't struggle or resist. In a passageway between, a Yeti approaches the Doctor carrying some kind of headset, and as it begins to lower it onto his head, he switches on his control box and the two Yeti become motionless. He takes the headset from the Yeti, makes some rapid adjustments to the circuits, and replaces it in the Yeti's grasp. He deactivates the control box, the Yeti return to normal, and they place the device on the Doctor's head.

Anne is reunited with her father, and Victoria asks about her friends. On the platform, Jamie is speaking into the microphone, attempting to bring the controlled Yeti to him. A Yeti appears, but though Jamie is unable to make it follow further commands, it does not harm him, but moves off back into the tunnels. As Jamie turns to leave, a Yeti is behind him.

Most of the group are now gathered in the Booking Hall, as the Doctor is ushered in, wearing the headset. As the Doctor again warns his friends away from interference, the Intelligence is heard thanking him for his cooperation. The Colonel yells out at the Intelligence to show itself, but it says that will happen soon enough. Chorley emerges, and as the entire assembly gasps at this, he desperately protests his innocence, exclaiming the identity of the real "traitor," Staff Sergeant Arnold.

The possessed Arnold appears, stating that it, the Great Intelligence, has manifested itself in his lifeless body. Jamie is brought in by a Yeti, and all the survivors are present. Arnold orders Jamie to stand by the Doctor where, suddenly, a Yeti's arms are around Jamie's neck. The Doctor protests and refuses further cooperation until Jamie is released, and it is ordered. The Doctor is then ordered to sit in the throne, as Arnold adjusts some circuits in the pyramid. A metal circlet is lowered onto the Doctor's head, attaching to his headset. As Arnold announces the beginning of the transfer, Jamie yells out for the controlled Yeti to attack. First it attacks its comrades, then Arnold, who is knocked out. As the transfer continues, the Doctor resists Jamie's attempts to rescue him. The Colonel assists Jamie as the Doctor's yelling and pleading to leave him alone are ignored, and soon the Doctor is free. Jamie hurls the headset into the heart of the pyramid, which explodes, causing the Yeti to collapse.

As the smoke clears and congratulations are exchanged, the Doctor is angry and despondent at Jamie and the others. He had altered the circuits so that instead of the Intelligence draining his mind, he would have drained the Intelligence. Instead of putting an end to its evil, it has simply been cut off from contact in space. They find Arnold's blackened husk of a body. Despite this, the Colonel and Anne are calling the Doctor a hero, and Chorley wants to make him a household name on his television program. That's all he needs to hear: he gathers Jamie and Victoria and, after hasty goodbyes, heads to Covent Garden and the TARDIS—hopefully before they start running the trains again.

[Source: TARDIS Wiki]