Dr. Emily Hartford finds herself dredging the depths of Lake Isabella—and her own past relationship—in What Darkness Does, the next thrilling mystery from Jennifer Graeser Dornbush.

Called in to investigate the body of a young mother found floating in a small Michigan lake, Freeport coroner Dr. Emily Hartford quickly determines that Samantha Browdey was murdered. Among the many questions circling this horrifying event is one that yanks hard on Emily’s heartstrings: Where is Samantha’s infant daughter? Working alongside police detective Isode Aditson, Emily becomes ferociously determined to find the missing baby, Brooklyn.

At the same time, Emily’s longtime boyfriend Nick Larsen has reappeared—after being missing, presumed dead, for over a year. But Nick has changed. Badly injured and severely traumatized, the ex-cop turned FBI agent is a different man, one who has endured unimaginable brutality and then buried his secrets deep. Nick has a long road ahead … but he’s not a patient man, and catching a sadistic killer seems like good enough therapy to him.

Emily has her doubts, but what’s clear is that a cruel killer’s reign of terror must be stopped, one way or another. Their foe is formidable, increasingly bold, and brutally reckless. To catch this monster, Nick must battle his own demons, while Emily puzzles together the mystery of Brooklyn’s whereabouts, in hopes of giving a grieving family a happy ending.