Mathilde, a young dancer with a promising career ahead of her, receives a letter from a "chain letter" as she is about to leave on a tour. On the way she reads to her friend Sophie all the disasters that supposedly should befall those who break the chain by not sending someone else the letter. Mathilde finds this funny and isn't worried at all. But on the first stop of her tour, the young dancer falls victim to a series of strange accidents.

A game show set and filmed on the real Fort Boyard in France. The contestants have to complete in physical and endurance challenges to win prize money.