Not long ago, Zuzanna Uritski was a cleaner at the 1893 Chicago World's Fair, Archibald Campion was the Fair's most imaginative engineer, and Elspeth was a lifeless automaton. But now? Now they're demon hunters, pursuing an ancient evil that has traveled across universes to take residence in one of history's most famous serial killers. Travel to an alternate history where no one is safe from demon possession, automatons are self-aware, and the world's greatest hope lies with a clever engineer, a dauntless young woman, and a paladin from another world.