Destination Tokyo

On Christmas Eve, the submarine USS Copperfin, under the command of Captain Cassidy, departs Mare Island Naval Shipyard on a secret mission. At sea, Cassidy opens his sealed orders, which direct him to proceed first to the Aleutian Islands to rendezvous with a PBY Catalina and take meteorologist Lt. Raymond aboard. He is then to proceed to Tokyo Bay to obtain vital weather intelligence for the upcoming Doolittle Raid.