The planet Skaro, the distant past. The Time Lords divert the Doctor, Sarah Jane and Harry to this war-torn world, and give the Doctor a mission: the evil of the Daleks is about to be born here, and the Doctor is to try to ensure they evolve into less lethally aggressive beings - or, failing that, to avert their creation altogether. But has even the Doctor the right to commit genocide?

The Doctor and Harry head to the Kaled city to alert the authorities to Davros' plans while Sarah Jane and Sevrin are forced to work on the completion of the Thals' rocket.