The old man PETTSON and his cat FINDUS live on a small farm way out in the countryside in Sweden. Christmas is approaching, and Pettson has given Findus the rash promise that THE TOMTE will come around with gifts for him at Christmas Eve. Pettson does not believe in the Tomte, but in order not to disappoint his cat, he decides to build an artificial Tomte - a mechanical TOMTE MACHINE. Pettson has a hard time keeping the project secret from Findus and getting the machine to actually work in due time. But somehow a mysterious magical force interferes...

Pettson and Findus are fishing down by the lake when suddenly a snowstorm rises and it starts to get dark. Lost in the bad weather they are forced to seek shelter in an igloo they build out of blocks of frozen fishes. Inside they tell stories from the past year to keep their spirits up.

Eccentric old farmer Pettersson and his cat, Findus, have hilarious adventures camping in the woods while waiting for a letter from the king.

A swimming machine turns up that has been doctored and modified into a tile thrower, but the machine malfunctions and causes an accident that imparts Pettson with amnesia. Suddenly, it seems as though the only hope for Pettson lies in old stories that will jog his memory, such as the tale about Findus getting lost as a kitten and the one about Pettson and Findus embarking on a thrilling treasure hunt.