Dr. Who and Sarah (Elisabeth Sladen) encounter trouble when they answer a distress call from the fringe of the universe. Braun: Terence Brook. Baldwin: Tony McEwan. Sorenson: Frederick Jaeger. Vishinsky: Ewen Solon.

With his new assistant Romana (Mary Tamm), the Doctor begins the search for the Key to Time. Dr. Who: Tom Baker. Voice of K9: John Leeson. Vynda-K: Paul Seed. Guardian: Cyril Luckham. Garron: Iain Cuthbertson. Unstoffe: Nigel Plaskitt. Binro: Timothy Bateson.

Returning to Earth, the Doctor and Sarah (Elisabeth Sladen) are met with hostility and suspicion. Crayford: Milton Johns. Morgan: Peter Welch. Styggron: Martin Friend. Kraal: Stuart Fell.

Arriving in London at the end of the 19th Century, the Doctor and Leela make friends with a police pathologist, Professor Litefoot, and learn that hairs taken from the clothing of a dead body found floating in the Thames seem to have originated from a very large rat.

The tracer brings the TARDIS to the planet Tara. Romana finds the fourth segment disguised as part of a statue but is then taken prisoner by Count Grendel of Gracht. Grendel is plotting to seize the Taran throne from the rightful heir, Prince Reynart, and has mistaken Romana for an android duplicate of the Prince's betrothed, Princess Strella, to whom she bears a remarkable resemblance. The Doctor is meanwhile captured by Prince Reynart's men Zadek and Farrah and taken to his hunting lodge, where he is forced to repair an android double of the Prince to act as a decoy for potential assassins.

The final segment of the Key is traced to the planet Atrios, engaged in a long war with the Zeons.

Exiled to Earth and forbidden from travelling by his fellow Time Lords, the newly regenerated Doctor arrives in Oxley Woods accompanied by a shower of mysterious meteorites. Investigating these unusual occurrences is the newly-formed United Nations Intelligence Taskforce (UNIT) led by Brigadier Alistair Gordon Lethbridge-Stewart. Most puzzling of all is the attempted kidnapping of a strange hospital patient, a man with two hearts who insists that he knows the Brigadier. Compiles episodes 1-4 from "Doctor Who" series 7

The Doctor and Romana discover the war is being co-ordinated by a computer called Mentalis.

The Doctor investigates the disappearance of the advanced aircraft Speedbird Concorde. Peter Davison, Sarah Sutton. Hayter: Nigel Stock. Tegan: Janet Fielding. Stapley: Richard Easton. Sheard: Brian McDermott.

Part 2. With The Doctor imprisoned by The Master, Martha endeavors to save the world.

Kylie Minogue joins Doctor Who to play Astrid, a waitress on a doomed spaceship that eerily resembles the Titanic. When a meteor hits, Astrid and The Doctor must protect the survivors from and prevent the whole ship from crashing to Earth.

Donna is determined to find the Doctor, even if it means braving Miss Foster and her hordes of Adipose.

The Doctor and Donna visit Pompeii in AD 79, on the eve of the eruption of Mount Vesuvius.

The Doctor takes Donna to her first alien world, but the Ood-Sphere reveals some terrible truths about the human race.

Part 1. Sontaran warriors set their sights on the Earth and its inhabitants.

Part 2. As poison gas suffocates the Earth's population, the Doctor and UNIT team members work to eliminate the threat.

The Doctor meets the most important woman of his life.

Agatha Christie's 10-day disappearance in 1926 may have been the result of amnesia, a nervous breakdown, or a giant alien wasp.

Part 1. The Doctor and Donna must uncover the truth behind the Nodes and the Data Ghost to uncover the library's secret.

Part 2 . As the shadows rise, the Doctor forges an alliance with the mysterious River Song.

The Doctor is trapped, powerless and terrified, on the planet Midnight, as a knocking on the wall begins.

Donna gets help from a mysterious blond woman.

Part 1. Earth's greatest heroes assemble to fight the New Dalek Empire, but a fearsome old enemy waits in the shadows.

Mars, 2059. Bowie Base one. Last recorded message: don't drink the water. don't even touch it. not one drop... Confused? All will be revealed in The Waters of Mars, starring Lindsay Duncan as the Doctor's cleverest and most strong-minded companion yet.

The newly regenerated Doctor and Amy Pond must save the world in less than 20 minutes from galactic policemen known as the Atraxi.

The Doctor and Amy travel to Britain of the future, where people live in a giant spaceship; Amy comes across the terrifying Smilers.

The Doctor and Amy meet Winston Churchill during a trip back to World War II, where they also encounter the Daleks.

Part 1. The Doctor hunts the last of the Weeping Angels through the Maze of the Dead; the mysterious River Song is back in the Doctor's life, but he doesn't know if he can trust her.

Part 2. The Doctor and his friends are forced to escape through the forest vault after they are surrounded by the Weeping Angels.

The Doctor suspects something isn't quite right with the daughters of the family that protects the streets of Venice.

The Doctor returns to Amy on the night before her first child is born.