In a movie studio, two cartoons are acting out a scene: Baby Herman, a lively and inventive baby, and his babysitter, Roger the rabbit, who gets into big trouble to get the little one out of risky situations. Despite his commitment, Roger does not satisfy the director with his interpretation: in fact, he is tormented by family worries, he fears that his beautiful wife Jessica is cheating on him with the owner of Cartoonia, Marvin Acme. Private detective Eddie Valiant, still penniless and half-alcoholic since his brother Teddy was killed five years earlier by a cartoon, is charged with finding evidence of the betrayal. Eddie manages to find what he was looking for and for Roger it is despair: he leaves the office of the producer Mr. Maroon in the grip of black desolation and nothing can be done to console him, Valiant who feels sorry for him. The police find Acme's body and immediately blame Roger...