The holiday episode airs Jan. 1 on BBC America.

This article contains spoilers for the upcoming Doctor Who festive episode.

Doctor Who star Jodie Whittaker announced in November that two of the show's core cast members — Bradley Walsh and Tosin Cole — will leave the science fiction saga after the upcoming special festive episode. While Whittaker is understandably unwilling to elaborate upon the circumstances of their characters' departures, she is happy to share how sad she felt filming her Time Lord's final moments with Walsh's Graham and Cole's Ryan.

"I was absolutely beside myself," says Whittaker, who effectively joined the the show at the same time as Walsh, Cole, and the fourth member of the main current cast, Mandip Gill. "I don’t have a poker face. It’s my actual job, so I should be better at it. But I remember when they called wrap on that day, Tosin was like, 'Calm Down!' I’d gone, I’d absolutely gone. In a way, it’s just reflective of the time we’ve had and this journey. I'm really lucky. Me and Mandip are still in the journey, but, because it was the end of us four, and us four have been so tight, it was one of those things. I know that in my life, this is one of the best things that will ever happen to me and the best times that I will ever have on set. This job is this thing that is untouchable. There’ll be a million other amazing experiences, hopefully. But if I do this for 20 seasons I know my first time as the Doctor was with this family as this four and this is our time — a Goonies moment, it’s our time! I felt very much like a kid in a well. I was so sad."

The last time viewers saw the Thirteenth Doctor her fate was left hanging in the balance as she was locked away in a high-security alien prison with no hope of escape. In the upcoming New Year’s Day special, Ryan, Graham, and Gill's Yaz are far away on Earth and having to carry on with their lives without her. However, they soon discover a disturbing plan forming. A plan which involves a Dalek.

"It’s the end of certain things but it also feels like a beginning as well," says Whittaker of the episode.

Whittaker is currently shooting the new season of Doctor Who but declines to discuss  — or, if the actress is to be believed, even think about — whether she will continue playing the Doctor after that.

"As far as I’m concerned, right now, I'm the Doctor and that’s taking up everything of me, as an actor," she says. "And to think something beyond that, I can’t put my head there, and I don’t want to."

The Doctor Who festive special airs Jan. 1 on BBC America. In addition to the regular cast, the show also features Dame Harriet Walter, Nathan Stewart-Jarrett, Chris Noth, and John Barrowman.

Watch the trailer for episode above.

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