In 1950, in a small village called Northern Station, Samuel, a young mailman and his girlfriend, Évelyne, spend hours replying to letters that children have sent to Santa Claus. While delivering the letters on Christmas Eve, Samuel dies of cold in the forest. He finds himself in the magic land of Santa Claus, where he becomes an elf in charge of answering Santa’s mail. Fifty years later, Samuel opens a letter from Satia, a young girl from Northern Station who asks Santa Claus if he will save her grandmother, who is seriously ill. With the help of his friend, Howie, the young elf decides to go to the village for grant the child’s wish. However, it turns out that Satia’s grandmother is none other than Évelyne.

A top-secret Soviet spy satellite -- using stolen Western technology -- malfunctions and then goes into a descent that lands it near an isolated Arctic research encampment called Ice Station Zebra, belonging to the British, which starts sending out distress signals before falling silent. The atomic submarine Tigerfish, commanded by Cmdr. James Ferraday (Rock Hudson), is dispatched to save them.