Episode list

Finding out-of-season Brighton beach somewhat lacking, the Doctor and Romana travel to the leisure planet Argolis - but there strange experiments are taking place.

Another man is found dead, strangled by the Doctor's scarf, so the Doctor is put on trial. By some of the archaic rules of law, he's made to "prove" his innocence by becoming a test subject in a new tachyon experiment with time. The result will prove his innocence or guilt, so they say.

With the Doctor suffering from the time experiment, the clandestine schemes of others start coming to light, along with the secreted purposes to which the tachyonic generator has been used.

With the saboteur and murderer revealed and arrested, peace should now be restored, but a new threat emerges - a war-monger who's both ready and eager to aggress upon other worlds with a newly manufactured warrior army.

The Doctor, Romana and K-9 arrive on the forest planet Tygella, where the native Tygellans now live in a underground city, due to the carnivorous plants. Where the Doctor finds he has been wrongly accused of stealing the Dodechedron, the city's power source. Only to discover the culprit is Meglos, the cactus-like last survivor of the desert planet Zolfa-Thura and he bids to return the Dodechedron to Zolfa-Thura for his own evil purpose and plans to use it as a powerful weapon and he plans to wipe out Tigella.

With the TARDIS occupants trapped in a chronic histeratic loop (forever reliving the same moment in time), the devious Meglos - disguised as the Doctor - gains the trust of the Tigellans along with full and private access to their power chamber.

With the dodecahedron gone, the city goes power critical. Its death, imminent. With Romana seeking escape from Meglos' pirates, and Meglos seeking escape from the sealed-up city, and the Doctor himself seeking to understand what's been going on (and why everybody wants him arrested), religious factions move in to take over the city.

With the Doctor about to be ritualistically sacrificed to appease the god Ti for stealing the dodecahedron, Meglos and the pirates return to Zolfa-Thura with the dodecahedron to fire up an ancient weapon and blast Tigella out of existence.

After receiving a summons from the Time Lords, the Doctor and Romana set course for Gallifrey, however the pair instead land on Alzarius where they cross paths with a rebellious but mathematically gifted boy named Adric.

The Doctor and K9 watch as Marshmen begin emerging from the water, while K9 follows them, the Doctor ventures on board the Starliner. Meanwhile Adric's gang attempt to hijack the Tardis with Romana on board.

The Tardis materializes on board the Starliner, reuniting Login with his daughter and allowing the Doctor and Adric to return to the cave to save Romana who is behaving strangely after being bitten by a spider.

As the Marshmen begin pouring into the Starliner thanks to an infected Romana, the Doctor and Adric hurry to create an antidote but in doing so discover a deep secret about the Marshmen and their connection to Adric's people.

The Doctor and Romana find an isolated planet. K9 scans the planet, finding it has a village. The Doctor and Romana find high technology readings with the TARDIS sensors even though the village appears to have an absence of technology. The TARDIS lands near the village. The Doctor and Romana set off, leaving K9 behind to guard the TARDIS. Adric, from the previous story, has stowed away on the TARDIS. K9 finds him, but Adric tells him that as he is a stowaway. The Doctor and Romana find two men arguing. The Doctor asks to speak to a scientist. One of the men mistakes them for lords. After the Doctor, Romana and one of the men leave, The other man, using a radio, calls to others and tells them of the two strangers who just arrived. Travelling through the forest, Romana and the Doctor are surrounded by men. They surrender and are taken to a hidden cave, where they meet the rebels. One man is trying to get a computer up and running. The Doctor helps him and Romana identifies the computer system as coming from Earth, Adric tries to steal some food in the village. Adric is caught and those who caught him take on pity him and offer him a place to sleep because of the evil things that happen at night. The Doctor and Romana appear to be attacked by a swarm of bats at the end.

The Doctor and Romana are taken to the tower where they meet The Lords and come to the realization that the tower is actually a disused spaceship. A Lord named Aukon arrives at the village and takes Adric with him back to the tower.

Tarak arrives to free the Doctor and Romana from their imprisonment. Believing The Lords to be vampires from Gallifreyan legend, the Doctor returns to the Tardis to consult the Record of Rassilon while Tarak and Romana search for Adric.

The Lords prepare to sacrifice Romana and induct Adric into their ranks as part of their plan to awaken the "Great One" and escape E-Space. Meanwhile the Doctor and K9 assist Kalmar's men in attacking the tower.

While the Doctor and Romana desperately rack their brains over how to escape E-Space, Time Winds strike the TARDIS, damaging it and K-9. Strangest of all, it allows Biroc, a hurt and hunted lion-man, to enter, phased in time, and set the control coordinates at zero-zero, sending the TARDIS into a milk-white void. Before running off, he warns of others who will be soon following.

Three humorless men from a damaged bulk freighter find the TARDIS. Wearily, Romana returns with them to appraise the situation of their damaged ship but, because she's a time sensitive, winds up as a living navigational component to replace their time-sensitive Tharil (lion-man) who escaped. Meanwhile the Doctor, having found a gateway, is having a time with Gundans, robot soldiers programmed to kill.

While Biroc leads the Doctor to a view of the Tharil's lordly past, Romana learns more about the damaged freighter and the coldheartedness of its crew. Meanwhile Commander Rorvik, confounded by the time mirror inside the universal center gateway, ignores evidence that it's no simple mirror and decides to blast it, imperiling the lives of everyone.

After the Doctor and Romana save the Tharil race, Romana agrees to leave the Doctor to become the Tharils' "Queen of Time."

The Tardis is drawn towards Traken, a harmonious planet. The Keeper of Traken appears inside the Tardis to warn the Doctor and Adric of his nearing death and of an evil being known as Melkur that threatens Traken's peaceful ways.

Tremas claims counselor privilege to protect the Doctor and Adric from execution, though it binds his fate to theirs if they're found guilty of murder. Melkur strengthens his hold over Kassia while Seron decides to have rapport with The Keeper to learn truth, and Adric finds evidence of another TARDIS in the area.

With Tremas falling under suspicion, due to his association with the Doctor, a new Keeper Nominate is named. Now, with everything in place, Melkur has only a short wait before his full malevolence can unfold.

With the merciless Melkur in control of The Source, the Doctor and his allies have only a slim chance of deposing him, which also puts the peace of the Traken Union in severe jeopardy.

Preparing to overhaul his TARDIS, the Doctor goes to Earth to take fresh measurements of a police box. A figure in white observes, as the Master lies in wait with a puzzling predicament for his rival Time Lord.

Figuring out that the Master has taken over Tremas's body, the Doctor and Adric land the Tardis near the River Thames before heading to Logopolis. Meanwhile a confused Tegan wanders the halls of the Tardis looking for help.

Adric, Nyssa and Tegan aid the Monitor in saving the Doctor after he is trapped inside his shrunken Tardis. The Master, posing as Nyssa's father Tremas, makes his presence known on Logopolis as his plan nears it's completion.

Forced to work together to save the universe from collapsing, the Doctor, the Master and Tegan use the Master's Tardis to travel to a giant satellite dish on Earth. Meanwhile Adric and Nyssa are taken to safety by the mysterious Watcher.