This is the second book of the Dresden Files series. The supernatural culprit this time is werewolves, as you might have guessed by the title. A few people show up dead, ravaged by not-quite-wolves, and Harry is called in to figure things out. He is first lead to a gang called the Streetwolves, nerdy college types who have decided to become werewolves and who are led by a not-at-all-human werewolf called Tera with a proclivity for walking around naked. He also finds a businessman who is cursed to become a wolf at the full moon and who has irked the mob boss from the previous novel. Also, a misunderstanding leads his cop friend to arrest him as an accomplice, making finding out which wolf did it a little more complicated.