While River Song takes Helen on an archaeological expedition like no other, the Doctor finds himself enlisted by an alien Queen to save her people.

Trapped and alone, Liv stares death in the face as she meets the enemy who’s been dogging the TARDIS travellers’ footsteps throughout Earth’s history.

The Doomsday Chronometer has been protected for five centuries: secret cults and societies jealously guarding its mystery. But what is their real purpose? The Doctor is about to discover the truth…