Investigating Loch Ness, the Doctor (Tom Baker) makes Zygons be bygones. Tom Baker, Elisabeth Sladen. Benton: John Levene. Munro: Hugh Martin. Duke: John Woodnutt.

The Doctor expels Leela to the wasteland. Borusa: John Arnatt. Andred: Chris Tranchell. Lord Gomer: Dennis Edward. Kelner: Milton Johns. Vardan: Tom Kelly.

The Fourth Doctor is an incarnation of the Doctor, the protagonist of the BBC science fiction television series Doctor Who. He was portrayed by Tom Baker for seven consecutive seasons and remains the longest-lived incarnation of the Doctor in the show's on-screen history, counting both the classic and modern series.

The Doctor takes Adric and a young air hostess named Tegan Jovanka, who has come aboard the TARDIS by accident, to the planet Logopolis, home of a race of mathematicians whose help he hopes to enlist in reconfiguring the outer shell of the TARDIS. The mysterious, wraith-like Watcher brings Nyssa from Traken to join them and warns of impending danger - something that is borne out as the Master arrives and kills a number of the Logopolitans.

The tracer detects the second segment on the planet Calufrax. The TARDIS makes a bumpy landing, and the Doctor and Romana soon discover that they are not on Calufrax at all. They are in fact on Zanak, a planet that has been hollowed out and fitted with engines so that it can transmat through space and materialise around others - such as Calufrax - to plunder their mineral wealth, leaving them as shrunken husks held by gravitational forces in a "trophy room".

A new threat is unleashed when the dome is destroyed. Tom Baker, Elisabeth Sladen. Sevrin: Stephen Yardley. Ronson: James Garbutt. Ravon: Guy Siner. Nyder: Peter Miles.

In the mysterious world of the Nethersphere, plans have been drawn. Missy is about to come face to face with the Doctor, and an impossible choice is looming… “Death is not an end” promises the sinister organization known only as 3W – but, as the Doctor and Clara discover, you might wish it was.

When the newly-regenerated doctor arrives in Victorian London, he finds a dinosaur rampant in the Thames and a spate of deadly spontaneous combustions.

A new threat is unleashed when the dome is destroyed. Tom Baker, Elisabeth Sladen. Sevrin: Stephen Yardley. Ronson: James Garbutt. Ravon: Guy Siner. Nyder: Peter Miles.

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.

The TARDIS is hijacked in the vortex by a time sensitive Tharil named Biroc, and brought to a strange white void. Biroc wants to free the others of his race who are being transported in a slave ship, captained by Rorvik, which is also trapped in the void. The only other thing present in the void is an ancient gateway leading to a decrepit banqueting hall.

In 1666 London, the Doctor (Peter Davison) discovers evidence of alien activity. Mace: Michael Robbins. Nyssa: Sarah Sutton. Terileptil Leader: Michael Melia. Adric: Matthew Waterhouse.

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.

Catch a sneak peek of the NEW season of Doctor Who!

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

Part 1. Scientists discover something isn't right beneath Earth's crust while drilling.

Part 2. Scientists discover something isn't right beneath Earth's crust while drilling.

Amy battles an alien in France with Vincent Van Gogh.

The Doctor investigates a mysterious staircase in a building where people can go up, but never down.

Part 1. A message on a cliff; a puzzle box that opens from the inside; the fates draw closer for the TARDIS.

Part 2. The fates draw close around the TARDIS.

Amy and Rory are trapped on a crashing space liner, and the only way The Doctor can rescue them is to save the soul of a lonely old miser. But is Kazran Sardick, the richest man in Sardicktown, beyond redemption? And what is lurking in the fogs?

Part 1. The Doctor, Amy and Rory receive a secret summons that leads them to the Oval Office in 1969. Enlisting the help of a former FBI agent and the irrepressible River Song, the Doctor promises to assist the President.

The TARDIS is marooned onboard a 17th-century pirate ship whose crew is being attacked by a mysterious and beautiful sea creature. Becalmed and beset by cabin fever, the pirates have numerous superstitious explanations for the Siren's appearance.

By following a Time Lord distress signal, the Doctor puts Amy, Rory and his beloved TARDIS in grave danger.

Part 1. A solar tsunami liberates doppelgangers from their human 'originals' in a futuristic factory. Can the Doctor prevent all out civil war?

Part 2. The Doctor must convince terrified factory-workers to work with their doppelgangers to overcome a monster of their own making.

The Doctor assembles an army to face the Battle of Demons Run - and River Song has something to tell him.

The TARDIS crash lands in 1930's Berlin, bringing the Doctor face to face with the greatest war criminal in the Universe. And Hitler.

Every child is scared of monsters, but George's terrified pleas for help reach the Doctor. Because George's monsters are real.

Amy is trapped in a quarantine facility for victims of an alien plague. Can Rory save her before she is killed by kindness?

With Cybermen on the streets of London, old friends unite against old enemies, and the Doctor takes to the air in a startling new role. Can the mighty UNIT contain Missy? As the Doctor faces his greatest challenge, sacrifices must be made before the day is won.