After the war is over, a radioactive cloud begins to sweep southwards on the winds, gradually poisoning everything in its path. Then a faint Morse code signal is picked up, transmitting from the United States and the submarine must set sail through the bleak ocean to search for signs of life.

After the war is over, a radioactive cloud begins to sweep southwards on the winds, gradually poisoning everything in its path. Then a faint Morse code signal is picked up, transmitting from the United States and the submarine must set sail through the bleak ocean to search for signs of life.