1983: Three hundred feet beneath the Atlantic, submarine Lieutenant Bill Guth receives the order he’s been dreading: a full nuclear strike against the USSR. Crisis is soon averted, but in the chaos that follows, one crew member ends up dead... 2019: Bill’s annual family gathering is interrupted when a historian turns up, eager to uncover the truth about the near-apocalyptic Cold War incident. Bill refuses to answer, but that night the man is brutally murdered. What happened all those years ago? How much is Bill to blame for events in the past? And who will stop at nothing to keep the secrets of 1983 where they belong?