En route to Kew Gardens, the Doctor and Peri are more than a little surprised when they land in the middle of a slag heap in England at the time of the Luddite uprisings. Unknown to the Doctor, his TARDIS has been dragged off course by the Master who plans to destroy his arch enemy once and for all, and pervert the course of history. But also present is the Rani, another exile from Gallifrey, who is conducting her own evil experiments on the humans of the nineteenth century. Soon the Doctor discovers that the female of the species is far, far deadlier than the male...