That is, until they meet a rather lively snowman and a mysterious stranger dressed in all red and white...
The Tenth Doctor and Donna are excitedly waiting for Christmas in the TARDIS, sipping hot chocolate. The Doctor decides to leave to get a Christmas tree in town. Once he and Donna get there, they realise it's been deserted, due to the heavy amount of snow. They notice a group of snowmen, which the Doctor is suspicious of.
Suddenly, the snowmen start chasing them. While running, the Doctor notices that both the snowmen and Donna have vanished. He hears Santa Claus laughing, but it quickly registers that this is a roboform. The Doctor pulls out his sonic screwdriver, and commands it to take him to the snowmen.
They arrive at an igloo, filled with snowmen and Santa-bots. The Doctor finds Donna in the middle of the crowd, tied up in tinsel, still with her mug of hot chocolate. The Doctor uses his sonic screwdriver to tie the snowmen and Santa-bots up in Christmas lights.
The Doctor saves Donna, and they escape on a sledge. As they sled down a snowy hill, Donna notices that a Christmas tree is following, and shooting baubles at them. The sled is hit, causing the Doctor and Donna to tumble out into the snow. Donna throws her hot chocolate at the tree, short-circuiting its wiring, as the Doctor looks for his sonic screwdriver - which is now buried in the snow.
Behind them, Santa starts chuckling. The Doctor and Donna believe he's a remaining roboform, and start throwing snowballs at him. He protests, revealing that he is the real Santa Claus. The Doctor apologises, but Santa brushes it off. He says he must be on his way, as the Doctor and Donna take the Christmas tree back to the TARDIS.
The next morning, in the TARDIS, the Doctor and Donna are opening their presents from Santa Claus. The Doctor receives a replacement sonic screwdriver, and Donna receives a hot chocolate machine, which the Doctor finds amusing.
- The Doctor and Donna watch a digital fire on a screen.
- Hot chocolate is Donna's "favourite thing in the world".
- The Doctor and Donna escape while evading a Christmas Tree that fires baubles at them. The Doctor has encountered a weaponised Christmas Tree before, (TV: The Christmas Invasion) and both he and Donna have previously encountered weaponised Christmas baubles. (TV: The Runaway Bride)