The TARDIS is stolen from Gatwick Airport, and when the Doctor and Jamie investigate they stumble into a trap set by Edward Waterfield, a time-traveller from the year 1866. His daughter Victoria has been kidnapped by the Daleks, in order to force him to lure the Doctor into their clutches. The Daleks have realised that human beings possess unique qualities which have enabled them to defeat the Daleks on every occasion the two races have fought; thus, the Daleks order the Doctor to monitor Jamie while he attempts to rescue Victoria, and synthesise the elusive Human Factor, which they intend to add to their own genetic makeup. The Doctor does so, and as he'd hoped, the test Daleks imbued with the Human Factor become playful and friendly. However, the Dalek Emperor then reveals that his real intention was to isolate the Dalek Factor and force the Doctor to spread it to the rest of humanity. The Emperor's plan fails, however, as the Doctor is not human and the Dalek Factor has no effect on him. The Doctor therefore tricks the Emperor into administring the Human Factor to several more Daleks, who begin to question authority and rebel against the Emperor. Waterfield dies saving the Doctor's life, and the Doctor and Jamie take Victoria with them as they depart, leaving the Dalek factions to fight each other to the death.
Aired: 1 Jul 1967