After the Doctor and his friends are exposed to a strange plague, Sarah becomes infected. Meanwhile, the Cybermen plan to destroy the planet of gold. Tom Baker, Elisabeth Sladen. Tyrum: Kevin Stoney.

The Doctor and Romana get a distresssignal from Chloris, a world with small quantities of metals.

Freddie needs a new coat for a "Doctor Who" fan-club event; Ash asks Freddie and Stuart for advice on winning back his ex-girlfriend; and Ash, Violet and Penelope make a shocking discovery during a shopping excursion.

The TARDIS is infiltrated by the Swarm - a space-borne intelligence that wishes to spread itself across the universe - and the Doctor is infected by its nucleus. The ship then materialises on Titan, one of the moons of Saturn, where the human occupants of a refuelling station have also been taken over.

Two alien seed pods are found buried in the Antarctic permafrost and the Doctor realises that they are from a Krynoid, a form of plant life that infects and transforms all animal life on planets upon which it becomes established.

The list of victims grows, but there is no trace of the killer. Tom Baker, Louise Jameson. Adelaide: Annette Woollett. Skinsale: Alan Rowe. Harker: Rio Fanning.

The Keeper of Traken" requests the Doctor's urgent help. Tom Baker. Keeper: Denis Cary. Adric: Matthew Waterhouse. Kassia: Sheila Ruskin. Luvic: Robin Soans.

The Doctor and Romana visit the Leisure Hive on the planet Argolis, the surface of which is uninhabitable following a twenty minute nuclear war between the Argolins and their enemies the Foamasi. The Argolins themselves are now sterile. Pangol, the youngest, was created by the Tachyon Recreation Generator, a machine that runs games in the Hive.

The killer reveals himself and battles Dr. Who and Leela. Tom Baker, Louise Jameson. Reuben: Colin Douglas. Vince: John Abbott. Skinsale: Alan Rowe. Adelaide: Annette Woollett.

The TARDIS arrives on a Minyan space craft, the R1C, commanded by a man named Jackson. Jackson and his crew are on a long quest to recover the Minyan race banks from a ship called the P7E which left their planet centuries ago. The Doctor helps to free the R1C after it becomes buried in a meteorite storm, but it then crashes into another newly-formed planet.

UNIT investigates when scientists go missing kidnapped by an alien trapped in the 13th Century. Travelling back in time in the TARDIS, the Doctor is unaware that he has stowaway.

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.

UNIT investigates when scientists go missing kidnapped by an alien trapped in the 13th Century. Travelling back in time in the TARDIS, the Doctor is unaware that he has stowaway.

The TARDIS arrives on the space liner Empress which has become locked together with a private ship, the Hecate, after colliding with it on emerging from hyperspace. The Doctor and Romana meet the scientist Tryst, who has with him a Continuous Event Transmuter (CET) machine containing crystals on which are stored supposed recordings of planets that he and his team have visited.

Freddie needs a new coat for a "Doctor Who" fan-club event; Ash asks Freddie and Stuart for advice on winning back his ex-girlfriend; and Ash, Violet and Penelope make a shocking discovery during a shopping excursion.

The Doctor is forced to land on Karfel, where the evil Borad plots to replace the inhabitants with a mutated life form. Peri: Nicola Bryant. Borad: Robert Ashby. Tekker: Paul Darrow. Vena: Jeananne Crowley.

Part 1. The Doctor finds an unusual hiding place.

Part 2. Smith and Jones are under siege.

When people start to disappear, a young woman finds cryptic messages bleeding through from a mysterious stranger called the Doctor.

Capt. Jack storms back into the Doctor's life; the Tardis travels to the end of the universe.

Part 1. Harry Saxon becomes Prime Minister, but has dark ambitions.

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

The overlap between quantum reality and science fiction is discussed.

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.