|Humphrey Bogart||Lt. Joe Rossi|
|Raymond Massey||Capt. Steve Jarvis|
|Alan Hale||Boats O'Hara|
|Julie Bishop||Pearl O'Neill|
|Ruth Gordon||Mrs. Sarah Jarvis|
|Sam Levene||Abel ''Chips'' Abrams|
|Dane Clark||Johnnie Pulaski|
Merchant Marine sailors Joe Rossi and Steve Jarvis are charged with getting a supply vessel to Russian allies as part of a sea convoy. When the group of ships comes under attack from a German U-boat, Rossi and Jarvis navigate through dangerous waters to evade Nazi naval forces. Though their mission across the Atlantic is extremely treacherous, they are motivated by the opportunity to strike back at the Germans, who sank one of their earlier ships.