The first official synopsis for Twice Upon a Time has been revealed on the BBC Store’s listing for the episode’s DVD and Blu-ray release.

The Christmas Special will mark Peter Capaldi’s final adventure as the Twelfth Doctor and will guest star David Bradley as the First Doctor and Mark Gatiss as the Captain. It will air on BBC One on Christmas Day and you can read the synopsis below.

Two Doctors stranded in a forbidding snowscape, refusing to face regeneration. And a British army captain seemingly destined to die in the First World War, but taken from the trenches to play his part in the Doctor’s story. This is the magical last chapter in the Twelfth Doctor’s epic adventure. He must face his past to decide his future. And the Doctor will realise the resilience of humanity, discovering hope in his darkest frozen moment. It’s the end of an era. But the Doctor’s journey is only just beginning.

One man, one destiny… twice. Watch the Twice Upon a Time Comic-Con trailer »