Spirou and Fantasio are spending a few days at Champignac Castle, keeping an eye on the estate while the Count is away visiting family. One night, as they are preparing to watch a comet pass in the sky, Fantasio\'s clumsiness causes them to lose consciousness. They awaken to the very noisy arrival of de Champignac aboard one of his strange machines - except that the old man claims to be not the Count himself, but one of his descendants... back from the future! 1 Illustrations, unspecified