Jim Butcher's The Dresden Files: Wild Card #2

A mysterious supernatural threat has invaded the Windy City, commanding the attention of Harry Dresden. Yeah, yeah - what else is new? Well, this one seems to be able to instantaneously extract the life force of its victims... a very rare ability that compels Harry to seek an audience with Lara Raith, head of House Raith and the White Court. Meanwhile, another powerful Chicago faction is targeted...