The film’s name suggests a different story than what unfolds on screen; its connection to submarines is minimal. Instead, it functions as an espionage thriller centered around Nazi spies who steal a model shortwave radio transmitter. This device allows them to communicate shipping locations to a submarine belonging to the Axis powers, which then targets those vessels. Facing this crisis, officials deploy their most skilled specialists in the field, hoping these experts can identify and locate the spies if former technicians are contacted for assistance with the radio’s operation. The remainder of the movie provides a fairly predictable wartime diversion – the outcome is clear from early on; the plot feels overly contrived, the lighting is substandard, and the production values appear low-budget. However, the cast, though not particularly memorable or outstanding, maintains a reasonable pace throughout the just over one hour runtime. "I don't bargain with rats"...!

Source on TMDB