David Tennant returns as the tenth Time Lord alongside another familiar face. Award-winning actress Catherine Tate is the Doctor's new companion as she reprises her role as Donna Noble from The Runaway Bride. Now reunited, the Doctor and Donna travel back to Pompeii in AD 79 on the eve of the infamous eruption where people are slowly turning to stone, they investigate a series of grisly murders with the help of Agatha Christie, journey to the home world of the sinister Ood and come face-to-face with an old enemy of the Doctor's.