The Rookie Club // Dead Center — Danielle Girard

A seasoned inspector in the Sex Crimes department, Jamie Vail is on a terrifying case: female officers brutalized by a stranger who leaves no clues to his identity and whose sick game is turning into a deadly vendetta. As she hunts a killer, who could be one of their own, Jamie's time is running out-because she's the killer's ultimate prize.

(Later re-released as Dead Center.)