Bitter Edge by Rachel Lynch

When a teenage girl flings herself off a cliff in pursuit of a gruesome death, DI Kelly Porter is left asking why. Ruled a suicide, there’s no official reason for Kelly to chase answers, but as several of her team’s cases converge on the girl’s school, a new, darker story emerges. One which will bring Kelly face-to-face with an old foe determined to take back what is rightfully his – no matter the cost.