Synopsis: Young Frédéric de Marck, 13, spends some time at the castle of his uncle, count Godefroid de Marck. He discovers there the secret of the "mechanical spectre" dying in the attic, in desperate need of new batteries. Built by the uncle, it had been instrumental in many assassinations and thefts, resulting in the old man's wealth. The unexpected death of the uncle prevents him from keeping his promise to get the spectre new batteries. This will cause his undoing when, many years later, Frédéric retires in the same castle and revives the long-forgotten contraption.