The Doctor turns up on a snowy planet at Christmas in the year 5343 where he bumps into a happy-go-lucky local called Nardole (Matt Lucas) and a very familiar face. He’s shocked to see his wife River Song (played again by Alex Kingston), but she doesn’t recognise him in his new older incarnation. So River is acting very differently in front of him now and he’s rather appalled at how she’s flirting with everybody else apart from him!
River mistakenly believes he’s the best medic in the universe and ropes him in to help her with something bizarre. She’s with King Hydroflax (Greg Davies), a large robotic creature, with a detachable head. Hydroflax has a precious secret diamond lurking inside his head and River’s desperate to get hold of it. But things don’t go to plan and the pair head off on a huge intergalactic chase, which sees them end up on a very strange spaceship where lizard-like creatures serve food to travellers…
It's aboard this spaceship that River finally works out who The Doctor really is, and together they complete the mission to retrieve the diamond from Hydroflax's head. In a very romantic last scene, the pair tell each other how they feel as they stand watching the most famous singing rocks in the universe...
