[4]In 1943 at the height of the Battle of the Atlantic, the Royal Canadian Navy Lieutenant Commander MacClain has just lost his ship and most of his crewmen due to enemy action.

He is allocated a new ship and while waiting for it to be built befriends Joyce Cartwright, whose brother Dick, an officer, was killed under his command.

MacClain's new Flower-class corvette is christened as HMCS Donnacona, and soon a crew of 65, including officer Paul Cartwright, Joyce's younger brother, is assigned to the ship.

The submarines below are still the main concern and when the Egyptian Star is torpedoed and sunk, MacClain attacks, sinking a U-boat with depth charges.

Before it sets anchor MacClain is asked to sail the Donnacona past the other ships in the harbor so that its crew may be saluted for their bravery.

Before final casts were announced, Robert Stack, Dick Foran, Diana Barrymore, Evelyn Ankers, Jon Hall, Nigel Bruce and Patric Knowles were considered by Howard Hawks.

In the June 11, 1942 issue of The Hollywood Reporter, Robert Rosson was to be the second unit director on the film, shooting 10 days on location in the Atlantic with a convoy, and Hawks was going to direct, as well as produce.

[5] The start of the film features Lieutenant Commander MaClain and his survivors from his previous ship on board a V&W class destroyer.