The Marsupilami, a mysterious animal that Spirou and Fantasio discovered in the jungle of Palombia, now resides in their local zoo. When he seems to drop dead suddenly, the reporters storm into the park demanding explanations. Much to everyone's surprise, though, the body has disappeared stolen! The two adventurers lose the thief after a night-time chase, but they will not abandon their friend, no matter where their loyalty may take them!
