The USS Pennsylvania, a ballistic missile submarine, departs Pearl Harbor on a routine patrol, led by Captain Josh Turnbuckle. As they submerge, nuclear war erupts on the surface. China initiates the conflict, with North Korea and Russia joining, leaving cities in ruins and civilization collapsing. Unaware of the apocalypse, the crew continues operations, believing communication failures are technical glitches, not realizing they have missed their orders to launch a counterstrike.
For 37 days, they remain isolated, grappling with personal fears and maintaining discipline. When they finally surface for communication, they are met with silence, prompting Turnbuckle to head back to Pearl Harbor for answers.
Upon arriva on day 61l, the crew finds Pearl Harbor obliterated, homes destroyed, and families gone. Rodriguez, desperate to find his family, escapes onto land, only to confirm the worst. Collecting supplies, the crew faces the grim truth that they are alone without command.
Turnbuckle decides to sail toward Kitsap Washington, hoping for survivors. Along the way, they discover more devastation and that organized gangs have taken over. After intense combat, they suffer casualties, realizing they face new threats beyond isolation.
