It’s nearly Halloween (Harry’s birthday) and Harry Dresden is less than thrilled to discover that his friend Police Lieutenant Karrin Murphy is going off to Hawaii with another man. He’s even less thrilled when Mavra, an extremely powerful vampire of the Black Court, who he hoped they’d managed to kill in Blood Rites, turns out not to be dead and is blackmailing him with Murphy’s involvement in the case unless he helps her. If Harry doesn’t find something called the Word of Kemmler in three days, Mavra will make sure Murphy’s career is ruined, and that she may very well face criminal charges because of aid she gave Harry on a mission against the Black Court vampires. Harry obviously can’t let that happen, and so he has no choice but to agree to the vampire’s demands.
Turns out the Word of Kemmler is a book, the last writings of a very powerful and very dangerous, now dead, necromancer and whoever possesses the book will gain access to terrible powers. Harry’s not the only one looking for the Word. Three of Kemmler’s former apprentices are in Chicago, wanting the to be the first to find the book and become the most powerful necromancer of them all.