Peter Capaldi is on his way out as the Twelfth Doctor, but he has one more adventure before his inevitable regeneration. At Comic-Con today, BBC unveiled the trailer for this year’s upcoming Christmas special. The Twelfth Doctor will meet the First Doctor (Game of Thrones alum David Bradley), and the pair will try to fix time itself — with a little help from the Doctor’s newest companion, Bill (Pearl Mackie).

Today’s Comic-Con panel was a chance for fans to say goodbye to Capaldi, who’s served as the Doctor for the last three seasons. Leaving with him is showrunner Steven Moffat, who’s handing the reins off to Broadchurch showrunner Chris Chibnall. All this paves the way for Jodie Whittaker to come aboard as the Thirteenth Doctor, the first woman to fill the role in the show’s storied history.

The Doctor Who Christmas special will air later this year.