It's 1942. America have just joined the war. Greyhound, an international convoy of 37 allied ships, is in operation. As Captain Ernest Krause leads his first command of a U.S. destroyer, the convoy ploughs through icy, submarine-infested North Atlantic seas. All the while hotly pursued by wolf packs of Nazi U-boats. Grappling with his newfound superiority and haunting self-doubt in 48 hours of desperate peril, Captain Krause's hopeless mission is doomed to fail. But armed with extraordinary courage and grit, hope may just be on the horizon . . .