James Bowen, a homeless busker and recovering drug addict, has his life transformed when he meets a stray ginger cat.

Ten strangers, drawn away from their normal lives to an isolated rock off the Devon coast. But as the mismatched group waits for the arrival of the hosts -- the improbably named Mr. and Mrs. U.N. Owen -- the weather sours and they find themselves cut off from civilization. Very soon, the guests, each struggling with their conscience, will start to die -- one by one, according to the rules of the nursery rhyme 'Ten Little Soldier Boys' -- a rhyme that hangs in every room of the house and ends with the most terrifying words of all: '... and then there were none.

The TARDIS crew take up residence near Rome in 64AD, where Ian and Barbara are kidnapped by slave traders, and the Doctor's imitation of Maximus Pettulian sees him taken to the court of Emperor Nero where he inadvertently plays a part in deciding the course of history...