This Doctor Who episode about the Daleks was apparently envisaged as providing an end and closure to the Doctor’s interactions with the Daleks. Of course, it was not to be, and one of the things about narratives involving time travel is that, even if one totally obliterates, defeats, or fundamentally changes an enemy at one point in time, they can still be encountered in their past. They would, however, be absent from the show for several years.
In “The Evil of the Daleks,” the Doctor’s TARDIS is stolen as a way of luring him into a trap, with the aim of getting him to conduct an experiment for the Daleks. The Doctor’s companion Jamie is made to try to rescue Victoria Waterfield, who is being held prisoner by the Daleks. As he does so, the Doctor takes readings of Jamie’s emotions and identifies the “human factor.” When the Doctor administers that human factor to some Daleks, they become playful and even call the Doctor their friend.It is then revealed that the aim of the experiment was not, as the Doctor had thought, to identify the human factor so that the Daleks could benefit from its supposed advantages. Rather, it was to help single out the Dalek factor and have that spread on Earth to turn human beings into obedient servants of the Daleks, like unto the Daleks themselves.
The tension is resolved when the Doctor tricks the Daleks into administering the human factor to significant numbers of Daleks. Once this is done, those Daleks begin behaving like human children – every time the emperor Dalek says something like “You must obey” the Daleks with the human factor as “Why?”
However implausible some elements of the story may be (such as the idea that some factor can so quickly turn one sort of entity into another), it still works as an exploration of the question of what makes us human, as well as the idea that ingenuity, compassion and friendship can make us stronger than powerful, obedient, xenophobic killers.
It also offers an intriguing exploration of whether, at the heart of what makes us human, is our willingness to question authority, whether of emperors or of parents or of deities. Is our penchant for asking “Why?” the quintessential component of the “human factor”?