Doctor Who: The Web of Fear

The TARDIS narrowly avoids becoming engulfed in a cobwebby substance in space. It arrives in the London Underground railway system, the tunnels of which are being overrun by the web and by the Great Intelligence's robot Yeti. The time travellers learn this crisis was precipitated when Professor Travers, whom they first met in the Himalayas some thirty years earlier, accidentally caused one of the Yeti to be reactivated, opening the way for the Intelligence to invade again.

Doctor Who: Spearhead from Space

The New Doctor arrives on Earth in the middle of a freak meteor shower. Faceless killer shop window dummies are coming to life and killing anything that comes into their path while Facsimiles are replacing top Military, Political and Civil leaders. The Nestene has come to invade the Earth. The convalescent Doctor teams up with Brigadier Lethbridge-Stewart and Dr. Elizabeth Shaw of UNIT to thwart the Nestine's plans even as the invasion begins.

Chronotrip

Philosophical Time Travel

Doctor Who: Day of the Daleks

Guerillas time-jump back from the 22nd century to assassinate Sir Reginald Styles - a diplomat working for World Peace, The Doctor discovers they are from a future where the Daleks have invaded the Earth (Following wars precipitated by Styles's destruction at the peace conference). With the Daleks desperate to maintain their version of history, The Doctor and Jo find themselves in a totalitarian future, where they must discover who really happened and prevent it.