Two years after the Civil War, Pinkerton agent Ed Morrow has gone undercover with one of the weird West's most dangerous outlaw gangs—the troop led by “Reverend” Asher Rook, ex-Confederate chaplain turned “hexslinger,” and his notorious lieutenant (and lover) Chess Pargeter. Morrow's task: get close enough to map the extent of Rook's power, then bring that knowledge back to help Professor Joachim Asbury unlock the secrets of magic itself. Because magicians, despite their awesome powers, have never been more than a footnote in history: cursed by their own gift to flower in pain and misery, then feed vampirically on each other—never able to join forces, feared and hated by all. But Rook, driven by desperation, has a mind to shatter the natural law that prevents hexes from cooperation, and change the face of the world—a plan sealed by unholy marriage-oath with the Mayan-Aztec goddess Ixchel, mother of all hanged men, who has chosen Rook to raise her bloodthirsty pantheon from its collective grave through sacrifice, destruction, and apotheosis. Caught between a passle of dead gods and monsters, hexes galore, Rook's witchery, and the ruthless calculations of his own masters, Morrow's only real hope of survival lies with the man without whom Rook cannot succeed: Chess Pargeter himself. But Morrow and Chess will have to literally ride through Hell before the truth of Chess's fate comes clear—the doom written for him, and the entire world, in A Book of Tongues.