While on a scouting mission to pinpoint flooding damage, officer Mattie Cobb and her K-9 partner Robo stumble upon a body floating at the edge of a lake. Robo catches human scent, which leads to an enigmatic forest-dweller who quickly becomes suspect number one. As the list of suspects grows, an unexpected visit from members of Mattie's long-lost family sheds new light on her childhood. The tangled threads of the investigation and family dynamics begin to intertwine - but darkness threatens to claim a new victim before Mattie and Robo can track down the killers.