Apidae by Xenia Melzer

No good deed—or good record of solving crimes—goes unpunished.
Detectives Andi Hayes and George Donovan of the Charleston PD are on vacation. Or at least they are until they are called back for an emergency: find Chief Norris’s missing son.

Fortunately, Andi’s insect spies lead him right to little Tyler Norris, who is safe and sound.
Unfortunately, along with the chief’s son, they find twenty-five corpses, victims of a serial killer who’s gone unnoticed for over a decade.
Chief Norris promptly cancels Andi and George’s vacation and assigns them as lead detectives on the case. Physical evidence leads them to a mental health facility where some of the victims received treatment, but Andi’s gift—his usual secret weapon—fails him. Promising leads and shady suspects all turn out to be dead ends, and they’re running out of time. Because the killer isn’t going to stop at twenty-five victims—and Tyler Norris has just gone missing again….