Plot

 

Part 1

 

On Earth, a small orange device is found on a grassy bank. Mr Ollis, the warden of the bird sanctuary, walks over to it and bends down to examine it. A Land Rover arrives at the cottage where Mr Ollis lives. A man steps out and knocks on the door. Mrs Ollis opens the door and the man introduces himself as Doctor Tyler. He asks her about the device and she tells him her husband is looking after it. The device is carrying an unusual energy blob that seems intent on capturing the Third Doctor. Tyler goes over to the area, and he and Mr Ollis site each other. Suddenly, there is a crackling noise from the device, and when Mr Ollis bends down to examine it, he vanishes. The birds fly off in panic. Doctor Tyler gets back in his Land Rover and asks to be put through to UNIT. He heads off to UNIT HQ and when he arrives, he meets with the Brigadier, the Doctor and Jo Grant. Tyler tells the Brigadier what happened and he tells him that he and the Doctor will be happy to help him. When Jo asks him what the box is for, he tells her it is for cosmic ray research. Tyler explains that even though he's not NASA, he still gets the results. Jo asks why the balloons are still being used. Doctor Tyler tells her that inside the device is the most advanced cosmic ray monitoring device between here and Cape Kennedy. Doctor Tyler tells the Brigadier he was going to contact UNIT for help. Doctor Tyler shows the Doctor some results which surprise the Doctor.

 

The Brigadier asks if there is anything they can do; at the Doctor's request, he hands a silicon rod to the Doctor, who proceeds to stir his tea with it. The Brigadier then specifies if there is anything U.N.I.T. can do about the space lighting. The Doctor tells him there is some sort of compressed light that travels faster. When the Doctor asks if the machine is working properly Doctor Tyler tells him it is, but he hasn't developed the latest plate yet. The Doctor tells him to develop it at once and then let him know. The Doctor and Jo go off to look for the balloon and Tyler tells the Brigadier he will be fine. He tells Tyler to make himself at home. When the Brigadier has gone, Doctor Tyler develops his plate but is horrified to see Mr Ollis' face. As Tyler goes to dismantle the box, the crackling sound is heard again and Doctor Tyler mysteriously vanishes, while a strange organism emerges from the sink plughole.

 

Meanwhile, Mrs Ollis is showing the Doctor and Jo the spot where her husband vanished. She then tells them the box had been there this morning, and that someone has already gone to collect it. The Doctor asks her if she has seen her husband since this morning. She says she hasn't. She tells them it's typical for him to go off on his own, but that he is always back in the evening. She says she will go and look for him if they like. The Doctor and Jo return to Bessie. Jo asks if it is important, and the Doctor tells her it is, "it's more important than I thought". Back at UNIT HQ, the Brigadier enters the lab with a full set of reports for Doctor Tyler. But he discovers Tyler has vanished. The Brigadier meets Sergeant Benton and asks him to find Doctor Tyler.

 

Outside, the Doctor and Jo are driving back to UNIT in Bessie. But as they get out, the organism appears. The Doctor orders Jo to get well back. They both run and Bessie vanishes in a flash of light. The Doctor and Jo return to the lab and the creature slides into the drain. In the lab, the Brigadier is waiting for Doctor Tyler when Sergeant Benton arrives and tells the Brigadier that Doctor Tyler is missing, and that there was an explosion in the garage. The Doctor comes in and clarifies that it was actually a flash of light. He tells the Brigadier that the drain needs guarding. Benton gives him a strange look, but the Brigader insists. Benton goes off to guard it.

 

The Brigadier tells the Doctor that Mrs Ollis called, saying her husband has not returned. He then tells him they have 1500 acres to cover. The Doctor tells him they don't have to look further because he has already found Mr Ollis - on the plate that Doctor Tyler was developing. The Doctor proceeds to take his sonic screwdriver out and search the area around the box they collected. He gets the strongest reading at the bottom of the sink. The Brigadier hands Doctor Tyler's reports over to the Doctor. He reads them and discovers that Tyler was right and someone has been scanning the Earth and takes an interest in UNIT. Jo reminds the Doctor that Bessie vanished. He also mentions the creature from the drain that was after them. It was a powerful organism with a very strong hunting instinct, directed at the Doctor. The Brigadier is in disbelief that the whole problem was for the Doctor. When the Brigadier asks why it took Mr Ollis, the Doctor says it was confused. Tyler was in the Doctor's laboratory, so the creature mistook him for the Doctor. It then took Bessie because the Doctor was near her at the time. He says there is a link between the beam and the organism. The beam was how the creature got to UNIT. The Brigadier asks if they can find it and the Doctor tells him that they don't need to. If they wait around, it'll find them.

 

Outside UNIT, a corporal stands next to a jeep. A new kind of creature covered in a rock like coating appears. The creatures starts advancing towards the corporal. Sergeant Benton arrives with more men and shoots the creatures. However, it is immune to bullets and it continues advancing. They also cause explosions. The Doctor notes that the creatures and the organism are from the same source, first the scout then the reinforcements.

 

Outside, Sergeant Benton realizes that force is useless and he contacts the Brigadier. The Brigadier orders a complete evacuation and afterwards, Benton must report to the lab. As the Brigadier leaves, the colored organism emerges from a vent behind him. Benton climbs through the window. Suddenly, the creature enters the room, and "eats" a table. The three friends rush into the TARDIS. The Doctor switches the TARDIS force field on. Benton stands in awe but refuses to state the obvious saying that nothing to do with the Doctor suprises him anymore.The Doctor tries to take off, but he can't. Someone is draining the power from the TARDIS. Considering it an emergency, the Doctor decides to contact his people, the Time Lords.

 

On the planet of the Time Lords, at the control centre, the President and the Chancellor know someone needs to help the Doctor. The Time Lords, however, have problems of their own: power drains. They are facing a force equal and opposite to their own. Unable to help the Doctor, they decide he can help himself. They summon enough energy to send the Second Doctor to help the Third.

 

In the TARDIS, the Third Doctor discovers a recorder that is strangely familiar. The Second Doctor appears out of nowhere and accepts it, thanking Jo. He then proceeds to criticize the TARDIS's new look and marvel at their problem. Jo is confused, but Benton happily greets the first Doctor he met. Jo demands an explanation, the Doctor, lost for a clearer explanation simply says "he's one of me". The Second Doctor insists that, on the contrary, the Third Doctor is "one of me". Benton confirms the story.

 

After Jo accept the story, the Second Doctor explains why he's there. The Second Doctor believes their capabilities have been doubled, but the Third Doctor insists it has been halved. Outside, the Brigadier and another UNIT soldier fire at the organism. Inside the TARDIS the two Doctors make contact to catch the Second Doctor up. They muse silently for a minute, then the Second Doctor proceeds to play Twinkle Twinkle Little Star on his recorder. They disagree.

 

The Time Lords, exasperated that they're not getting along, send the First Doctor to keep them in order. He appears on the TARDIS's screen, and tells the other two Doctors it's a time breach, to stop delaying, and cross it. Jo asks who that was. The Doctor answer in unison "me", then turn to each other and insist, "me!" They flip a coin, the Second Doctor switches off the TARDIS force field, and the Third goes outside. Jo follows him and before she can stop him, they are both are engulfed in a blinding flash from the plasma creature in the U.N.I.T. laboratory...

 

Part 2

 

The  Second Doctor warns Sergeant Benton not to go outside because the Third Doctor knows what he's doing, "At least I hope he does". Benton worries about the Third Doctor and Jo, but the Second Doctor assures him they've simply been transported somewhere else. The two of them marvel at the creature's sudden inaction. Benton wants to "take the opportunity to blow it to bits" but the Doctor insists on a subtler approach. They exit, peering at the organism.

 

The Brigadier appears and the Doctor tells him to leave it alone because it's not dangerous at the moment. The Brigadier processes what he just saw, then turns and stares at the Doctor. Benton tells the Brigadier "it's the first one". The Brigadier wonders why the Doctor changed his appearance back, and what happened to Ms. Grant (Jo). The Doctor explains but he doesn't believe him. The Doctor tells him that changing into "the tall thin fellow" hasn't happened to him yet, and that he's a temporal anomaly. The Brigadier insists that the Doctor mucked around and changed his face back, but says he just wants Ms. Grant back. The Doctor can't make any promises, so the Brigadier tells him to talk to his all-powerful superiors. The Doctor says they aren't all-powerful right now and that it's been left up to "me and me and me."

 

The Time Lords argue over the Doctor helping himself, and the force they are combating. The limited power has resulted in limited success in transporting the First Doctor. The Second is helping UNIT, and the Third is in the black hole.

 

The Third Doctor and Jo find themselves in a barren desert like landscape. Meanwhile, the Second Doctor is at a loss with how to deal with the creature or contact the Third Doctor. However, the Doctor decides to "keep it confused" and harmless and wonders if he has a television set handy. On the barren world, the Third Doctor and Jo explore. They find debris from the lab, including Bessie and a trail of footprints.

 

In the UNIT lab, the Doctor and Benton have created a device to subdue the creature. The Brigadier appears. He wants the Doctor, posing as the Doctor's assistant, to explain everything to his superiors. They leave, but Benton disturbs the creature and the device does not subdue it. The Brigadier and Doctor return and together they flee into the TARDIS. The Brigadier stands in awe. The Doctor says he'll get used to it. The Brigadier, however, believes the Doctor has been using UNIT equipment to build the TARDIS. The Doctor says they come like this.

 

The Third Doctor and Jo follow the footprints and find Doctor Tyler. The Doctor explains they are on a stable planet in the black hole, "an anomaly inside an impossibility." A mysterious man looks at a screen that depicts the three of them talking and orders a rock-like creature to bring his guests to him. The three are promtly interrupted by several of the creatures.

 

Inside the TARDIS, the Second Doctor concludes that his plan had the opposite effect because the creature is anti-matter. The Brigadier tells him to stop his nattering; the Doctor looks for his recorder. The Brigadier demands to be let out, but the Doctor explains that he can't. All they can do it think, and he needs his recorder to do so. In the anti-matter universe, the Third Doctor and his two companions are escorted into a palace.

 

The Second Doctor tries to augment the Brigadier's radio, and comments that he envies the Third Doctor and the adventure he is probably having as he does so. The said Doctor is arguing with Tyler, who wants to make a break for it. Despite the Doctor's efforts to stop him he does. Tyler ends up running in circles and ending up back where he started. In the TARDIS the Brigadier tries out his augmented radio. The First Doctor appears on the screen. He confirms that the Time Lords are struggling. He tells the Second Doctor to take the force field down.

 

In the anti-matter universe, the Doctor and Tyler conclude that their bodies have been processed so they can exist in the anti-matter universe, just like the organisms who could exist in UNIT's world. Meanwhile in the TARDIS, the Second Doctor says that he is taking the force field down, much to his companion's dismay. Benton points out that if he does so the creature can get at the TARDIS. The Doctor replies "precisely," and does so. As he does so, the creatures outside of UNIT disappear. The UNIT soldiers fighting the beings are left standing in confusion.

 

Part 3

 

Meanwhile, on the planet, the Third Doctor, Jo and Doctor Tyler enter the throne room. Jo asks who brought them here and a loud booming voice declares: "I did!" From the shadows steps the legendary Time Lord, Omega. He was the solar engineer who created the supernova that powers Time Lord civilization, but was considered killed in the explosion.In actuality, he had been transported to the antimatter universe, where his will and thought turned the formless matter into physicality. Trapped, due to the fact that his will is the only thing maintaining reality, he vowed revenge on the Time Lords who left him stranded. Omega sends Tyler and Jo away. While in the cell, they muse about the relationship between the Doctor and Omega. Elsewhere, Omega asks the Doctor for help in defeating the Time Lords, threatening death for the Doctor and his companions if he refuses.

 

In the TARDIS, the Second Doctor tells the Brigadier to prepare himself for a shock. Once leaving the shelter of the machine, the Doctor muses at how the Head Quarters came with the TARDIS. The Brigadier opens the door to find the barren anti-matter landscape and returns to the Doctor, upset that he's stolen HQ and they're in a new country. Benton tries to explain that they're in a different universe, but the Brigadier leaves. The Doctor tries to look for his recorder, but he and Benton are chased off by a rock creature. Outside, the Brigadier encounters Mr. Ollis. He explains that there were others here, but they were taken by the rock creatures. Right on cue, several appear, escorting the Doctor and Benton into Omega's palace.

 

Inside, the Third Doctor urges Omega to simply return to his spot on the Time Lord high council and do no more harm. Just then, the Second Doctor and Benton arrive. Omega demands to know who they are, but the Third Doctor insists they are innocent bystanders. Omega objects that the organism was programmed to seek out a Time Lord and proceeds to deduce that one of the two newcomers must be one. Because the Second Doctor does not fear him, he figures out that they are the same Time Lord. Omega is angered that they deceived him and sends them away. Outside, Ollis and the Brigadier fail to find any way in except the main entrance.

 

In the cell, the Doctors disagree briefly, until the companions rebuke them. They apologize. They also repeat the "me" escapade when Tyler inquires who the Second Doctor is. They also proceed to explain the Law of Singularity and how Omega is controlling the world with the pure force of will. Jo tells them they ought to be able to put their heads together to will up a door. They do so, leave, and tell their companions to stay put. Tyler says he wants to see the 'singularity chamber' and follows, Benton and Jo close behind.

 

The Doctors arrive and discover a column of smoke. "Singularity!" they marvel. Omega suddenly appears, raving mad. They explain that they put their wills together to escape. Omega challenged the Third Doctor to fight the Dark side of his mind.

 

Meanwhile, the companions lose track of the Doctors, as well as their way, but find their way out of the palace. As they leave, they run into the Brigadier and Ollis. Together, the five flee to Bessie and back to UNIT headquarters.

 

The Time Lords speak to the First Doctor, telling him all three Doctors are needed to defeat Omega. They send him into the black hole, using the last of their power.

 

Omega and the Third Doctor fight until the Third Doctor is thrown into a black void in the dark side of Omega's mind, helpless. Omega's avatar gets the Doctor in a stranglehold and Omega declares: " THOSE WHO OPPOSE THE WILL OF OMEGA SHALL NOT LIVE! DESTROY HIM!"

 

Part 4

 

Omega defeats the Third Doctor in the black void of his mind. Back in reality, the Second Doctor helps the Third Doctor to his feet. Omega reveals that he has summoned the Doctors here to take over the mental maintenance of the antimatter universe so he can escape. He tells the Second and Third Doctors that without him, there would be no time travel. He and the other Time Lords would be locked away in their own time.

 

However, the Doctors discover that years of exposure to the corrosive effects of the black hole's singularity have destroyed Omega's physical body - he is trapped forever. Omega walks over to a mirror and takes off his mask. He discovers that he hasn't got a head or a physical body. The Third Doctor replies: "You exist only because your will says that you exist. And your will is all that is left of you." Omega bows his head and then lets out a insane cry. Driven over the edge by this discovery, Omega now demands that the Doctors share his exile.

The Second Doctor tells Omega that if he destroyed the Third Doctor, he would destroy his only chance of freedom. Both Doctors escape briefly, and receive another message from the First Doctor, urging them to put their heads together and figure out how to outsmart Omega. After this psychic conference, they agree to remove the force field generator of the TARDIS. As the Second Doctor opens up the TARDIS console base to disconnect the apparatus, he exclaims at the sight of his lost recorder. However, the Third Doctor suggests that the recorder is even more important than the generator itself. Realizing he intends to sacrifice his musical instrument, the Second Doctor protests until the Third Doctor promises to get him a replacement, even a thousand.

 

The Doctors contact Omega and discuss a means to satisfy him. They agree to meet him directly once more. Fearing that this could turn ugly, the Third Doctor tells Jo she must follow his orders without question, even if they betray her compassion. The Doctors then offer Omega a proposition. They will give him his freedom if they send the others back to the positive matter universe. Omega agrees, and the others begin to file out into the transporter Omega creates. Ollis and Dr Tyler depart, followed by a reluctant Benton. Jo, fearing she won't see him again, refuses to leave the company of the Third Doctor until he comforts her with a reminder to trust him. She enters the light beam, then the Brigadier gives the Doctors a salute and joins her. When everyone has departed save them, the Doctors offer Omega the force field generator containing the Second Doctor's recorder, which had fallen in it prior to the transport through the black hole.

 

When the Third Doctor shouts at Omega to take the generator, Omega is angry at the Third Doctor for commanding him to do it. He knocks the generator over in a rage and the unconverted positive matter recorder falls out of the force field. The Second Doctor screams for his successor to run and the two make a break for the TARDIS. When the recorder comes into contact with the antimatter universe, it annihilates everything in a flash, returning the Doctors in the TARDIS to the positive matter universe.

 

The group returns to Earth inside UNIT HQ, with everything back where it was. Jo weeps over the apparent loss of her Doctor while the Brigadier mourns the losses of both incarnations he knew. However, the TARDIS reappears in the laboratory and the Doctors emerge, with Jo hugging the Third Doctor earnestly. They explain that because the recorder fell into the force field, it was not turned into antimatter, giving them a chance to escape and cause a reaction that turned the black hole into a supernova, igniting a brand new star for the Time Lords to use as an energy source. When Omega's will collapsed, it made all the objects that had ended up in his world return to their proper places. For the Doctors, it was the TARDIS, and for Ollis, the lakefront with his shotgun, explaining his absence.

 

With the power now restored to the Time Lords, they are able to send the First and Second Doctors back to their respective time periods. The First Doctor appears on the TARDIS monitor one last time to bid his future incarnations farewell, fearing what they would do without his incarnation's intellect. The Second Doctor then gives a cheerful goodbye to his friends, old and new, and admits he enjoyed meeting his successor, though his future self jokingly hopes they won't meet again. The Second Doctor vanishes into thin air to the amazement of Dr Tyler. The Brigadier and Benton leave the TARDIS to "make a full inventory of the HQ" and see if anything disappeared after these events. Benton questions him about what they would document the cause of the lost items if they found any, but the Brigadier simply tells him to come along, obviously using this as an excuse to get away from the madness he's been through. Dr Tyler also exits the TARDIS, jesting that he cannot write about this in any academic sense if he values his job.

 

Now that only he and Jo are still inside the TARDIS, the Third Doctor begins to have a moment in private, quietly regretting that he had to send Omega to his demise. Jo sees his remorse and assures him not to feel guilt because he had no other choice but this when Omega put everything in the universe at stake. The Third Doctor, wishing he could have found a way to release Omega of his fate in a humane way, explains that death was the only freedom anyone could offer Omega.

 

Fortunately, the Doctor is given a reason not to be dispirited over his actions when he hears the unmistakable hum of TARDIS materialization technology inside his own TARDIS, and a familiar device appears on top of the time rotor. It is a new dematerialisation circuit for the TARDIS to replace the faulty one keeping him stuck on Earth. He also notices he can remember the dematerilisation codes for the device and all his blocked memories have come back. The Time Lords have rewarded the Doctor for the feat of heroism he has demonstrated for the whole of his race by gifting him with this new circuit, and restoring his knowledge of how to travel through space and time. The Doctor is happy that his people have forgiven him and granted him his freedom, but Jo sadly states that he'll probably be rushing off now. The Doctor assures her that he won't be leaving just yet, since he needs to construct a new force field generator...

 

Meanwhile, Ollis arrives home and his wife responsibly asks him where he has been. Ollis tells her she wouldn't believe him if he told her, and asks if supper is ready.