Peter Capaldi's Doctor is coming to an end - and the first look of the Christmas special teases it could all be down to Mark Gatiss.
The actor, who has also written for the show, will take on the mysterious role of The Captain in the show's seasonal one-off - which will be Capaldi's final moments in the TARDIS.
In another telling moment, it looks like the Time Lord will be going back to where it all began - with the first ever incarnation of The Doctor making a reappearance.
It'll be more than 50 years since this version of the Doctor was seen on screen, and will be played by Harry Potter's David Bradley.
The new episode, called Twice Upon a Time, sees Capaldi come face-to-face with his past, and was teased for the first time during Children in Need last week.
Fans of the show were given a sneak peek at the festive episode, where Capaldi, Gatiss and Bradley were united on screen as they all appeared on the TARDIS.
The World War I pilot, known only as The Captain, was perplexed by his surroundings, asking: "Am I going mad?"
Peter replied: "You're an officer for WW1 at the south pole being pursued by an alien through the arctic".
As the pilot got even more confused that there could have been more than one world war, the first incarnation of the doctor finally realised he was looking at himself.
After Capaldi bows out during the episode, he will be replaced by Jodie Whittaker - the first ever woman to play the role.
Jodie is expected to make her debut by appearing at the end of the festive special.BBC America had previously teased what will become of the show, with the synopsis on their website reading: "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."
The end of the 12th Doctor was put in motion at the end of last series - when he flew to a frozen land in order to die.
In the desolate land, he shouted: "I don't want to change again, never again, I can't keep on being somebody else. I'm staying. I will not change. I am the Doctor."
But he was answered by a figure who emerged through the snow saying: "No, no, no, I am the Doctor, the original."