Get caught up with the full season now On Demand, the @bbcamerica app, or BBC iPlayer.
The Battle of Ranskoor Av Kolos
As the New Year begins, a terrifying evil is stirring from across the centuries of Earth’s history. As the Doctor, Ryan, Graham and Yaz return home, will they be able to overcome the threat to planet Earth?
Who is the mysterious commander with no memory? What lies beyond the mists? Who or what are the Ux?
A battlefield, a conflict-scarred survivor, and a deadly reckoning await the Doctor, Ryan, Yaz and Graham.