This momentary distraction, unfortunately, doesn't help them escape -- especially when the rest of the base's crew barges in with guns while most definitely looking at and thinking about the sleepers. They're rescued -- of course! -- by Santa, who blasts his way into the base (he's preceded by a parade of slinkys and toy robots) and sends the sleepers back to bed with a clap of his hands. ("It's Christmas Eve! Early to bed.")
Though there's a lot of disbelief in the room, Santa's charisma -- and encyclopedic knowledge of what everyone got for Christmas as a child -- seems to convince everyone. And, as Santa himself points out, they have bigger problems: these alien face-huggers are actually dream crabs, and if there are many of them on earth the human race could be facing its last day -- and last Christmas. And when Santa asks if you want to help him save Christmas, you say yes... even if you're the Doctor.
That Makes Perfect Sense, Right?
These face-huggers send their victims into a dream, where they stay while the crabs slowly devour their brains. These telepathic aliens mean they can't trust anything they see, since it could be these dream-crabs messing with their minds. The problem with telling the reality from the fantasy, however, is that their real lives are pretty odd to begin with. After all, the Doctor traveling space and time in a blue box isn't actually any stranger than Santa Claus being real... so how do you tell reality from fantasy?
The truth is, you can't. We quickly find out that the entire crew of the station, plus the Doctor and Clara, are already under the influence of these dream crabs, and they have to fight to recognize what's real and what isn't to remember the real lives they have to go back to. This is makes for some interesting, Inception-style dream-within-a-dream narrative... but it also makes the plot senselessly convoluted in a way that has become a trademark quality of Steven Moffat's episodes. Just how all of them got into this dream when they're a group of unrelated (save the Doctor and Clara) people who have never met? How did they all wind up in a shared -- and horrifying -- dream about an alien invasion? Like many Moffat stories, the narrative starts to break up the more you think about it... so our advice is not to think about it too hard, but instead to enjoy the episode's great character moments, of which there are many.
A Dream within a Dream within a Dream
Being stuck in a dream world means that Clara encounters Danny again, having a perfect Christmas with him. But even in this dream version of Danny prioritizes keeping Clara safe over anything else, and when the Doctor manages to barge into Clara's dream, Danny's the one who talks her out of believing the world around her. It's one of the best moments of the show... and maybe the entirety of the season.
Do you know why people get together at Christmas? Because every time they do it might be the last time. Every Christmas is last Christmas... and this is ours.
The entire scene is a tear-jerker moment, not just for fans of Danny and Clara, but for anyone who's celebrated Christmas without someone this year. That sense of loss echoes throughout the episode, making it feel like a melancholy reflection of times past, even as the episode wraps itself in the silliest trappings of the Christmas season.
It's enough to wake Clara up, but only to realize that they're trapped in another dream. They were saved, originally, by Santa.... but Santa's not real and is, instead, part of the dream. Still, being an amalgam of what everyone thinks of as Santa Claus, Santa is actually trying to help them find their way out of the dream world.
You're a dream who's trying to save us?
I'm Santa Claus. I think you just defined me.