Gunner (Chavis) sets out on a quest to save his ill mother (Dawson) by searching for a mythic figure who possesses the secret to immortality, the Water Man. After enlisting the help of a mysterious local girl, Jo (Miller), they journey together into the remote Wild Horse forest — but the deeper they venture, the stranger and more dangerous the forest becomes. Their only hope for rescue is Gunner’s father (Oyelowo), who will stop at nothing to find them and in the process will discover who his son really is.