Grave Peril is the third installment in the series, published in September 2001. It is available in paperback (now with new cover art by Christian McGrath), in audio format (read by James Marsters and released by Buzzy Multimedia), and in the Sci-Fi Book Club onmibus Wizard For Hire with Storm Front and Fool Moon.
The following blurb is printed on the back cover:
Harry Dresden's faced some pretty terrifying foes during his career. Giant scorpions. Oversexed vampires. Psychotic werewolves. It comes with the territory when you're the only professional wizard in the Chicago area phone book.
But in all Harry's years of supernatural sleuthing, he's never faced anything like this: the spirit world's gone postal. All over Chicago, ghosts are causing trouble - and not just of the door-slamming, boo-shouting variety. These ghosts are tormented, violent, and deadly. Someone - or something - is purposely stirring them up to wreak unearthly havoc.
But why? And why do so many of the victims have ties to Harry? If Harry doesn't figure it out soon, he could wind up a ghost himself… .
This book introduces Knight of the Cross Michael Carpenter, his wife Charity and the rest of the Carpenter family, Father Forthill, the Leanandsidhe, Thomas Raith, Justine, Mavra, and Duke Paolo Ortega.