Written by David Whitaker
Directed by Derek Martinus
The TARDIS has been stolen by antiques dealer Edward Waterfield, who lures the Doctor and Jamie into a trap. They are transported back to Waterfield's own time, 1867, where his daughter Victoria is being held hostage by the Daleks to ensure his cooperation in an unknown experiment.
The Daleks force the Doctor to monitor Jamie's performance of a test, the rescue of Victoria, with the supposed intention of identifying “the human factor”: the special quality possessed by humans that enables them always to defeat the Daleks. The Doctor, having succeeded in this task, implants the human factor into three test Daleks, resulting in them becoming friendly and playful!
Everyone is transported back to Skaro where the Doctor discovers that the Daleks' true aim has been to isolate “the Dalek factor”, the impulse to destroy, and implant it into humans, creating a race of allies that will serve their aims. The Emperor Dalek informs him that his TARDIS will be used to spread the Dalek factor throughout all time.
However, through a ruse, the Doctor is able to infect many more Daleks with the human factor. A civil war breaks out between the two Dalek factions and they are apparently all destroyed. As Waterfield has been killed during the battle, the Doctor offers Victoria a place aboard the TARDIS. From a hill-top, Jamie, Victoria and the Doctor watch the Dalek city in erupt in flames as the civil war continues. The Doctor pronounces this as the final end of the Daleks.Though in the rubble of the city, the lights from a lone overturned Dalek begins to pulse…
Troughton's inaugural season concludes with an absolute classic, an epic battle against the programme's definitive foes that was meant to kill them off for the foreseeable future. Terry Nation was at this point putting all of his energy into setting up a Dalek TV series with NBC in America, and this meant the implacable monsters weren't going to be available for Doctor Who. The Evil of the Daleks was meant to give them an epic send off, and as Nation was too busy with negotiations to write the story, the scripting duties went to former script editor David Whitaker.