In the world of rare books everything has its price. But when the book is a satanic tract, the currency is not money but life. A well-know bibliophile is found hanged days after selling a rare manuscript of Alexander Dumass classic, The Three Musketeers. Across Madrid, Spains wealthiest book dealer has finally laid his hands on a 17th-century manual for summoning the devil. Lucas Corso, solitary and obsessive, is the detective hired to authenticate both texts. But the further he follows the trail of devil worship, the more it leads him back to Dumas. Hes the unwitting protagonist in someones evil plot, but is he sleuth or hero, Sherlock Holmes or dArtagnan?