From the BBC:

Still reeling from their first encounter, can the Doctor and her new friends stay alive long enough, in a hostile alien environment , to solve the mystery of Desolation? And just who are Angstrom and Epzo?

(via Doctor Who News)

The Doctor and her new friends have barely had a chance to recover from their first adventure together before they are plunged into another - which will take Graham, Ryan and Yasmin on their first journey to an alien planet. The unlikely travelling companions are faced with a struggle for survival as they try to solve the mystery at the heart of this strange, dangerous new world. (Radio Times)