White Night - Jim Butcher

Wizard Harry Dresden must investigate his own flesh and blood when a series of killings strike Chicago's magic practitioners in this novel in the #1 New York Times bestselling series.

Someone is targeting the members of the city's supernatural underclass-those who don't possess enough power to become full-fledged wizards. Some have vanished. Others appear to be victims of suicide. But now the culprit has left a calling card at one of the crime scenes-a message for Harry Dresden.

Harry sets out to find the apparent serial killer, but his investigation turns up evidence pointing to the one suspect he cannot possibly believe guilty: his half-brother, Thomas. To clear his brother's name, Harry rushes into a supernatural power struggle that renders him outnumbered, outclassed, and dangerously susceptible to temptation.

And Harry knows that if he screws this one up, people will die-and one of them will be his brother...