Seething, the Lt. Cdr is determined to take vengeance for deaths of those men who were mercilessly gunned down by a German U-boat. He refuses the Admiral’s offer for leave, and decides instead to wait until a new ship is commissioned. Whilst he’s on standby, he befriends Joyce Cartwright, played by Ella Raines, the sibling of Dick Cartwright, an officer who lost his life on the ship under McLain’s command.
Quite naturally disturbed by the loss of her brother, Joyce pins the blame for his tragic and untimely death on Mac; she is heartbroken and believes that if it weren’t for him - Dick would still be alive. However, time heals the ugliest wounds, and gradually, her animosity towards Mac fades, and is replaced with love.
In the meantime, the HMCS Donnacona, a Corvette K 225 is commissioned with a crew of sixty five men, which includes Joyce’s young sibling - Lt. Paul Cartwright, a typical youngster who complains about what a hard act to follow and please MacLain is. The ship is bound for Europe, under the command of Commodore Ramsay, tasked with the duty of carrying cargo such as airplanes, gasoline and tanks. The Germans are stationed off the coast of Newfoundland, at Ethel, when another ship is torpedoed - the HMCS Donnacona sights the remnants – dead soldiers who have been thrown to the surface from the bowels of the ocean.
On the ninth day, the HMCS Donnacona is caught in the midst of a raging storm, as a result of which, it strays from the convoy and is lost. When the ship is about three hundred miles away from the Irish Coast, MacLain realizes there are more ships like the HMCS Donnacona which have strayed away from their convoys, he meets the Captain of the tanker Egyptian Star, who conveys dire warnings and fears to MacLain, believing that his ship is being followed and is under surveillance of German submarines.
Just as the Captain warned, they come under German fire from a squadron of bombers, but one of the convoy’s fighter planes comes to its rescue. In the fighting that ensues, the Egyptian Star is sunk by a torpedo, while the HMCS Donnacona takes on the submarines. Using a depth charge, one of the submarines is eliminated, however, the HMCS Donnacona comes under attack from a U-boat in a surface battle that disables it, Mac is also injured. Lt. Paul Cartwright with Seaman Stooky O’Meara move underwater to dispose the depth charges, which strike the submarine.
When it’s destroyed, MacLain recognizes the U-boat as the one which was responsible for the death of his men. The HMCS Donnacona arrives safely in Ireland with another six merchant ships. As a mark of respect, before it anchors the Corvette K 225 sails past the other docked ships, which salute the crew for its unsurpassed courage in the face of the enemy. A film which has a tragic beginning, but a triumphant end; an easy watch if you’re a WWII movie buff!