A crew of low-rent Paris thieves break into a decrepit mansion expecting easy treasure, but instead uncover a hidden Nazi vault, a deceptive caretaker, a long-dormant doomsday device, and the monstrous crocodile guarding it. When the weapon is accidentally activated – and the creature swallows the only way to stop the countdown – it rampages into the neighbouring Bois de Boulogne park, trapping tourists and families on a lake island. With authorities shrugging off the danger, this unlikely group must improvise rescues, confront their own failings, and battle tooth-and-scale to save strangers and each other.