Miles beneath the ocean floor, a drilling station tremors violently. A deep-sea earthquake? No. Something far worse. Dr. Cillian Bradley, leading a routine research mission, witnesses the station breached by a monstrous, unseen force. With their escape pod crushed, Cillian and a handful of survivors, including the green Paul, must navigate a labyrinthine network of tunnels, their pressurized suits their only defense against the crushing darkness and the ever-present threat of the Leviathan. As they fight for survival, Cillian must confront her inner demons and harness her knowledge of the deep to outsmart the creature before it picks them off one by one.