Inspector Marotte, attending an auction of rare collectible books previously ownded by the recently murdered M. Le Duc de Poisse, hopes he can catch his old nemesis Prahec, a murderer and book thief. More murders occur at the deceased's estate when it is learned that a rare first edition of the Gutenberg Bible is hidden on the premises. Among all the friends, relatives, and servants gathering at the estate, Marotte is finally able to reveal the identity of Prahec and apprehend the guilty.