Young Liam still believes in Santa Claus and, in order to prove his existence to his friends and parents, he writes a letter to the kind wizard. However, due to a frustrating typo, the message reaches a completely different recipient - Satan. Flattered by such attention from the prince of darkness, he immediately arrives at Liam's house in hopes of ruining Christmas and sowing chaos. He promises Liam to fulfill all his wishes, of course, in exchange for his immortal soul. Unexpectedly, a real friendship develops between him and the boy, which is capable of softening the heart of even the most hardened villain.