Plot

 

The Fifth Doctor, Tegan and Turlough are taking a break at the Eye of Orion, one of the most tranquil spots in the universe. In the TARDIS, the Doctor has just finished renovating the control room. Turlough is sketching. Tegan is enjoying the peaceful atmosphere. It's a change from their non-stop adventures that leave them no time to relax. He goes outside to join his companions and enjoy the peace and quiet. When Tegan wonders why it is so restful there, the Doctor explains that it is because of the bombardment of positive ions.

 

Elsewhere, in a hidden chamber, a dark figure manipulates the controls of a Time Scoop and kidnaps the First Doctor as he walks through a rose garden. The dark figure takes a figurine of the First Doctor from a window and places it on one of five spots on a diorama, which lights up in response.

 

Back on the Eye of Orion, the Fifth Doctor feels a pain in his chest, but dismisses the thought that anything is wrong with him as Turlough and Tegan look worriedly at him.

 

Elsewhen, Brigadier Lethbridge-Stewart is at a UNIT reunion, talking to his replacement Colonel Crighton about his former scientific adviser, the Doctor; it seems that UNIT had been unable to track him down for the reunion. The Brigadier says, "Wonderful chap - all of them", confusing his replacement. The Second Doctor bursts through the door and is happy to see his old friend. As they talk on the yard about their times together, the Second Doctor tells the Brigadier that he must go as he is bending the Laws of Time. However, they are snatched up by the Time Scoop. Models of them appear in the window and the dark figure puts them in the slot next to the First Doctor.

 

The Fifth Doctor feels another pain and collapses after reassuring Tegan and Turlough that everything's all right.

 

Elsewhen, the Third Doctor is driving his vintage car, Bessie. He notices the Time Scoop coming towards him. He tries to evade it, but is taken anyway, appearing as a figure in the window and placed into the next slot in the diorama.

 

The Fifth Doctor tells his companions he must get back to the TARDIS. There is something definitely wrong with his past and he is in immediate danger. As he puts it, "A man is the sum of his memories, a Time Lord even more so". He is nearly to the TARDIS when he collapses in pain as his third incarnation is snatched. He tells his companions he has to find "my other selves..."

 

Sarah Jane Smith is about to leave home. K9 warns her not to, as the Doctor is involved in a strange occurrence and insists she take him with her. Unfortunately her car is out of action and she has to take the bus. Believing K9 is overreacting, she dismisses his worry and heads off.

 

Somewhen else, the Fourth Doctor and Romana are enjoying a punt along the River Cam in Cambridge. They are Time Scooped by the dark figure as well. However, to the growing anger of whoever is taking the Doctor's incarnations out of time, he cannot take the Fourth Doctor and Romana from the window as figures. They have been trapped in a time eddy in the time vortex and do not rematerialise.

 

Waiting at the bus stop, Sarah is snatched by the Time Scoop, and her figurine placed in the diorama alongside the Third Doctor.

 

The Fifth Doctor and his companions have entered the TARDIS. After setting a destination on the console and starting the TARDIS off he collapses thanks to his immediate past life being trapped in a time eddy. He begins fading into the Time Stream, but Tegan and Turlough keep him in existence by encouraging him. The TARDIS lands, and the scanner shows a desolate, rocky landscape - the Death Zone on Gallifrey.

 

All the Doctors and their companions, save the Fourth Doctor and Romana, have actually been deposited on a desolate, rocky landscape — the Death Zone on Gallifrey. Figures of the Fifth Doctor, Tegan and Turlough have been placed in the diorama section next to the First Doctor - the spot where the Fourth Doctor and Romana should have gone is blinking.

 

Meanwhile, in the Capitol on Gallifrey, the Inner Council of Time Lords, headed by Lord President Borusa and consisting of Chancellor Flavia and the Castellan, are in session. Despite the regenerated and still arrogant Borusa's misgivings, the High Council has voted unanimously to call in the Master to go into the Death Zone to help the Doctors. They explain that the Eye of Harmony is being drained by whomever is taking the Doctors out of time, endangering all of Gallifrey. Offered a pardon and a new cycle of regenerations if he rescues the Doctors, the Master accepts. He is given a copy of the Seal of the High Council by the Castellan to prove his credentials and a transmat recall device. He is transmatted to the Death Zone.

 

In the Zone, the Doctors face many dangers. The First Doctor finds himself in a hall of mirrors and is reunited with his granddaughter, Susan. Their reunion is cut short when a Dalek arrives and tries to kill them. They trick the Dalek into destroying itself by pushing it into a dead end, where its energy weapon ricochets and destroys it; as the Doctor points out, "It's very dangerous to fire energy weapons in an enclosed area!" The Second Doctor and the Brigadier escape from a squad of Cybermen, and the Third Doctor rescues Sarah from her fall down an embankment. Sarah is confused; she had watched the Third Doctor regenerate into the Fourth (Planet of the Spiders), but is glad to see the Doctor she once knew.

 

The Second and Third Doctors explain to their companions that in Gallifrey's past, known as the Dark Time, the Time Lords greatly misused their powers. A device called the Time Scoop plucked beings out of their times and placed them in the Death Zone, where they fought each other in a sort of gladiatorial game for the Time Lords' amusement and entertainment. The Doctors' goal now is to reach the Dark Tower, where the Time Lord founder Rassilon is entombed, although there is some doubt as to whether Rassilon is actually dead.

 

The Master meets and fails to convince the Third Doctor he is there to help. He flees when thunderbolts fall from the sky. The Third Doctor only sees this as confirmation this is all a plot of the Master's, especially when another thunderbolt disables Bessie. The Doctor and Sarah are forced to continue their journey on foot.

 

The First Doctor and Susan find the TARDIS; the presence of the First Doctor seems to stabilize the Fifth for the moment. Together, they scan the tower and find three entrances — one at the apex of the tower, the main gate at the base and one underground, but a force field prevents the TARDIS's entry, or even it moving within the Death Zone. The Fifth Doctor takes Tegan and Susan towards the main gate, but encounters the Master, who has no better luck convincing the Fifth Doctor of his bona fides than he had the Third. At that moment, the two are surrounded by Cybermen. When they try to run away, the Master is knocked out by a cybergun blast. The Fifth Doctor finds the Master's recall device on his unconscious body and transmats himself to the Capitol. Tegan and Susan start back to the TARDIS to warn the others, but Susan trips and sprains her ankle and needs Tegan's help.

 

In the Capitol, the Fifth Doctor is informed of the situation by the High Council. The Doctor realises he has done the Master an injustice and that they were found too easily by the Cybermen. Like the Daleks, the Cybermen were never brought to the Death Zone in the Dark Times because they fought too well. He opens the recall device and finds a homing beacon inside. The Castellan (who had given the device to the Master), is arrested, and his office and quarters ordered to be searched.

 

Tegan and Susan have told the First Doctor what happened to the Fifth Doctor. The First Doctor decides to head for the main gate himself. Tegan insists on accompanying him, much to his dismay. Susan and Turlough remain in the TARDIS to wait for the Tower forcefield to be deactivated so they can move the ship there.

 

The Master, confronted by the Cybermen, offers himself as a guide to the Tower in order to save his life.

 

While waiting for the First Doctor and Tegan to get to the Tower, thumping is heard outside the TARDIS; the scanner reveals a squad of Cybermen carrying a coffin-like box and lots of cables.

 

A box containing Black Scrolls of Rassilon, forbidden knowledge from the Dark Times, has been found, supposedly in the Castellan's quarters. The scrolls spontaneously combust before anyone can examine them, and Borusa orders the Castellan taken for interrogation, authorising the use of the mind probe - much to the Castellan's horror. However, as the Castellan is escorted outside, there is a shot and a cry. The Doctor rushes out to find the Castellan dead, a gun by his hand; the Captain of the guard reports he was shot while trying to escape. President Borusa refuses to allow the Doctor to return to the Death Zone and orders Flavia to look after him.

 

The Second Doctor and the Brigadier are exploring a series of caves in the hope of reaching the lower entrance to the Tower when they encounter a Yeti, apparently left over from the previous games. Taking refuge in an alcove, the Doctor tries to chase the Yeti off with a firework, but only maddens it, causing it to collapse the entrance to the alcove. However, the Doctor detects a breeze blowing further back, and discovers the underground entrance to the Tower.

 

The Fifth Doctor voices his concerns to Chancellor Flavia — while the Castellan was stubborn, he was devoted to his oath of office and could never have been a traitor. Plus, his reaction to the Scrolls was not that of a guilty man, but sheer disbelief. The traitor is still at large. Flavia decides to have a word with the Captain, while the Doctor will speak with Borusa.

 

On the surface, the Third Doctor and Sarah come across a Raston Warrior Robot, according to the Doctor "the most perfect killing machine ever devised". Able to move with blinding speed and fire bolts of metal at its targets, it detects its victims by motion. The Doctor and Sarah cannot move without attracting the robot's attention, but luck is on their side when a squad of Cybermen come over the ridge and are eliminated by the robot. Taking advantage of the distraction, the Doctor and Sarah run past the robot, taking some rope and spare bolts from its cave.

 

The First Doctor and Tegan reach the main door and open it using an entry coder hidden under a large bell.

 

Reaching a cliff face just above the Tower, the Doctor uses the rope and bolts for a grappling hook. He and Sarah abseil across the gap to the top of the Tower, to the amusement of the Master far below.

 

On the main floor of the Tower, the First Doctor and Tegan find a chessboard floor blocking their way. The Doctor quickly determines the chessboard is a trap — electrical bolts will destroy anyone attempting to cross unless they find the safe path. The Master appears at this point, warning them the Cybermen are close behind. While the Doctor and Tegan hide, the Master lures the Cybermen onto the chessboard, where all but the CyberLeader (who waited behind) are killed by the trap. He also tricks the CyberLeader into trying to cross with him before fatally blasting him with a Cybergun. Enjoying this little piece of butchery, the Master blithely steps across the board, moving into the Tower after telling the Doctor that "it's as easy as pie." The Doctor realises that the Master means the Greek letter pi and the safe path is calculated by means of the mathematical constant. Armed with this knowledge, the Doctor and Tegan make their way across the trap.

 

In the Death Zone, the TARDIS is now surrounded by Cybermen, who start to assemble a bomb to blow it up. Inside, Turlough and Susan watch helplessly, not knowing what to do.

 

The Second and Third Doctors encounter more obstacles while moving separately through the Tower, with the mind of Rassilon emitting intensifying fear. They also encounter what appear to be their previous companions, the Third meeting Captain Mike Yates and Liz Shaw and the Second Jamie McCrimmon and Zoe Heriot. The Doctors soon realise they are just phantoms to impede their progress through the Tower and the spectres vanish with a scream. The First Doctor blithely ignores the fear as an illusion, considering that "at my age, there's little left to fear!"

 

Finally, the first three Doctors reach the tomb: Rassilon's sepulchre. While the Brigadier, Sarah and Tegan get re-acquainted, the three Doctors try to translate an inscription in Old High Gallifreyan on a pedestal near a control panel - squabbling amongst themselves as usual.

 

The Fifth Doctor finds Borusa has vanished from the Council Chamber, but the guards insist the President could not have gotten by them at the only entrance. The transmat is out of power, so the Doctor deduces there must be a secret door and orders the guards to notify Flavia that the President has disappeared. After an intensive search, he realises that the Harp of Rassilon, standing in the Council Chamber, is the key and that a tune will open the door. He starts experimenting.

 

In the tomb, the Doctors have deciphered the inscription. Rassilon had discovered the secret of immortality. He was willing to share it with whoever overcame the obstacles to the tomb and took the ring from his body and put it on. However, a line troubles the First Doctor, who wonders just what it means: "To lose is to win and he who wins shall lose." The Master steps out of the shadows to claim immortality himself, but is attacked from behind by the Brigadier and tied up by Sarah and Tegan.

 

The Fifth Doctor realises that the tune is shown in a painting of Rassilon playing the Harp, where the sheet music is clearly depicted. He plays the tune, which opens the door. The Doctor enters the secret chamber and finds the dark figure that had taken his other selves out of time: Borusa. The Lord President is not satisfied with ruling Gallifrey for his lifetimes — he wants to be President Eternal and rule forever. Like the first three Doctors, Borusa has determined that Rassilon discovered the secret of immortality and he means to claim it, sending the Doctors into the Zone to clear the way of obstacles for him. Using the Coronet of Rassilon, Borusa overwhelms the Fifth Doctor's will, forcing him to obey his commands.

 

The Third Doctor fixes the control panel by reversing the polarity of the neutron flow, allowing the TARDIS to transport itself to the tomb just seconds before the Cybermen's bomb detonates.

 

The Second Doctor contacts the Capitol. The Fifth Doctor answers, still under Borusa's control, and tells his other selves to await his and Borusa's arrival. The First and Third Doctors are suspicious, but the Second doesn't believe them. Transmatting to the tomb with the Fifth Doctor, Borusa paralyzes the Doctors' companions with a command and tries to control the minds of the First, Second and Third Doctors. However, they combine their wills against him to free the Fifth Doctor. As Borusa declares that Gallifrey will believe its President's word over that of the notorious renegades, a booming voice echoes through the chamber. It is Rassilon, demanding to know who disturbs him. Borusa steps forward to claim his prize of immortality and, while the other Doctors protest, the First Doctor holds them back, telling Rassilon that Borusa deserves the prize. Borusa takes the ring from the body and puts it on, but finds himself paralyzed, then transformed into one of several stone faces carved into the side of Rassilon's bier. He has found his immortality, but not the way he wanted it.

 

After asking the Doctors if they want immortality too - all four frantically say "No!" - Rassilon frees the Fourth Doctor from the time vortex before sending the Master back to his own time, saying that "His sins will find their punishment in due time. After telling the Doctors to say their goodbyes, and that they have chosen wisely, Rassilon returns to his eternal rest as the companions find themselves released from Borusa's psychic hold. The First Doctor smugly tells the Fifth that he finally understood the proverb "To lose is to win and he who wins shall lose". The prize was yet another trap — a means for Rassilon to discover who wanted immortality (and were thus a danger to Gallifrey) and get them out of the way.

 

The Doctors and their companions say their good-byes to each other - with a few snipes between the Doctors - and re-enter the TARDIS, save for the Fifth Doctor, Tegan and Turlough. As the three watch, the others are transported back to their proper timezones - Rassilon used temporal fission to send them home. Chancellor Flavia arrives with guards and tells the Doctor that with Borusa's disappearance, the Council has appointed the Doctor as President. The Doctor orders Flavia back to the Capitol, saying that he will follow in his TARDIS and she has full powers until his return. Once in the ship, however, he tells Tegan and Turlough he has no intention of returning. Tegan asks if the Doctor really intends to go on the run from his own people in a "rackety old TARDIS." The Doctor replies, smiling, "Why not? After all, that's how it all started..."