In her bed on Christmas Eve, a little girl reads an illustrated storybook entitled "The Monster's Christmas" to her teddy bear, as something sneaks around in the trees outside her window. She hears a noise in the other room, and thinking that it's Father Christmas, she goes to investigate. Instead she finds one of the monsters from her book, who has come to find someone to help defeat an evil witch that has stolen the voices of all monsters; because they sang better at Christmas carols than she did. The little girl agrees to help, and armed with the contents of her Christmas stocking sets out on a surreal, imaginative, electronically sounded, novelly avant-garde, one-of-a-kind, brain-tickling, foam-monster populated outdoor fantasy adventure through smoky fields, magical forests, boiling, bubbling mud pools, volcanic landscapes and secret witch mountain cave lairs.
Jack Terry is a master sound recordist who works on grade-B horror movies. Late one evening, he is recording sounds for use in his movies when he hears something unexpected through his sound equipment and records it.
Rémi is a man trapped in a deteriorating marriage. When his wife is unexpectedly killed in a car accident, Rémi is left with his stepdaughter, Marion, who chooses to stay with him rather than live with her birth father.
Frank is an expert professional safecracker, specialized in high-profile diamond heists. He plans to use his ill-gotten income to retire from crime and build a nice life for himself complete with a home, wife and kids.
To win the right to marry his love, the beautiful princess Andromeda, and fulfil his destiny, Perseus must complete various tasks including taming Pegasus, capturing Medusa's head, and battling the Kraken monster.