Ally Lane is the pilot and navigator of the The Betty Loo, a search and rescue submarine. She took refuge from her demons on the sub a decade ago.

Brian Kingston, a captain with good intentions but a heavy drinking problem, jumps at the opportunity to make more money than he can imagine on a deep-sea dive aboard the search and rescue submarine, The Betty Loo. He quickly discovers just what he's gotten himself, and his crew, into. The Betty Loo will be going to suicidal depths on a mission to rescue The Peacemaker, a sub once thought to be unsinkable. After receiving an anonymous threat on the day of departure, Brian is left with no choice but to continue on the mission.

But the depths of the sea aren't the only problems ahead. New crewmembers arrive, and seeds of distrust are sown within hours. And, upon arrival to The Peacemaker, he realizes that though not all the bodies are dead, there is no one to rescue.

The crewmembers, both old and new, have to trust one another and fight for their lives against the adapting undead or join them in the floating graveyard that is The Peacemaker.