Resurrection of the Daleks

From: http://www.bbc.co.uk/doctorwho/classic/episodeguide

The TARDIS becomes caught in a time corridor but the Doctor manages to free it and it then materialises in present day London within sight of Tower Bridge. Investigating some nearby warehouses, the travellers stumble into a trap that the Daleks have set for them.

The Daleks also attack a space station orbiting Earth in the future. Their aim is to rescue their creator, Davros, who has been held there in suspended animation since his capture by humanity. They want him to help them find an antidote to an anti-Dalek virus created by the Movellans.

In addition, the Daleks have constructed android duplicates and installed some of them in key positions of authority on Earth. They now intend to send duplicates of the Doctor and his companions to Gallifrey in order to assassinate the High Council of the Time Lords.

These plans ultimately fail, however, as one of their duplicate humans, Stien, rebels and destroys the space station. Davros is unable to find a cure for the virus but has an escape pod ready in case of problems.

Commander Lytton, an alien mercenary working for the Daleks, escapes to Earth. Tegan, sickened by all the killing she has seen, decides to remain on her home planet.

21 out of 94 (22.3%) raters say this story requires a previous story.