Jake (Douglas Smith) and his wife Elle (Isabelle Fuhrman), who has recently fallen ill, have been in constant misery since the death of their son Raymond. Wrecked with the guilt of feeling that Raymond’s death was Jake’s fault, Elle has never managed to forgive him. When Elle, believed to have drowned in the pond, mysteriously returns, the retreat descends into a waking nightmare as an insidious parasite takes hold and sinks them into a terror where the boundaries of love, guilt, and survival blur.