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.
David Tennant plays the Doctor and Freema Agyeman plays his companion Martha Jones. Thelma Barlow and Mark Gatiss guest star.
Setting: LazLabs, Southwark Cathedral
Enemies: The Lazarus Spider
Best Guest: Mark Gatiss/ Thelma Barlow
Best Moment: Lazarus chasing the Jones sisters
Worst Moment: None!
Best FX: The Lazarus Spider
Did you spot...: Martha's references to her past travels.