Night Light (2013)

When some of Chicago's minor magical talents become the targets of abuse, the police chalk it up to isolated incidents of self-inflicted harm, but Chicago's only professional wizard cannot, even though he's off the books for this one. No one has hired Harry Dresden to investigate. Then it starts to look serial, and Harry won't wait for someone to die in order to declare this a case. He's planning a solid preemptive strike against whomever or whatever is stalking the city's most vulnerable practitioners. Set between "Proven Guilty" and "White Night."