The war is over. Nobody won. Only the inhabitants of Australia and the men of the U.S. submarine Sawfish have escaped the nuclear destruction. Captain Dwight Towers (Gregory Peck) takes the Sawfish on a mission to see if an approaching radiation cloud has weakened, but returns with grim news; the cloud is lethal. With the days and hours dwindling, each person confronts the grim situation in his or her own way. One (Fred Astaire) realises a lifetime of Grand Prix ambition, another (Ava Gardner) reaches out for a chance at love. The final chapter of human history is coming to a close...