Our take
A horror film borrowed for Christmas, with face-grabbing crabs at the North Pole, dreams within dreams and Nick Frost as a swaggering, practical Father Christmas. The scares are real and the BBFC gave it a 12, but under them is a tender story about grief and letting go, and Clara's dream reunion with Danny is quietly devastating. Probably the most Christmassy of the specials, and one of the scariest.
What happens
At Christmas the paths of the Doctor and Clara cross again, and Santa Claus turns up too, with his elves. Together they go to help a scientific team at the North Pole whose base is under attack from Dream Crabs, creatures that latch on to a person's head and give them dreams while they devour the brain. Santa keeps appearing to help, which makes no sense at all, and slowly it becomes clear that nobody can trust what they are experiencing: the whole adventure is a series of dreams inside dreams, and Santa is a dream trying to save them. In one of those dreams Clara meets Danny Pink again, and he gives her permission to move on. There is a sleigh ride across the London skies, a glimpse of Clara as an old woman, and finally a real waking that gives the Doctor and Clara another Christmas together.
Can the kids watch it?
Rated 12 by the BBFC for moderate horror and threat, the only 12 among the Christmas specials we checked; too frightening for most under-10s.