Is it the parting of the ways for the Doctor (David Tennant) and Martha (Freema Agyeman)?

Martha returns home as Russell T Davies’s Doctor Who continues. Could this be the end of her travels with the Doctor? When she discovers her family is caught up in the scheming of Professor Lazarus and his Genetic Manipulation Device, it becomes a fight for survival, as human DNA twists into monstrous form.

Thelma Barlow and Mark Gatiss guest star.

Saturday 5 May
6.45-7.30pm BBC ONE