A radio reporter begins to suspect that a commentator at his station may be using her position to broadcast shipping information to enemy spies. With the help of the girl’s sister, he sets out to expose the spy and her Nazi gang. (IMDb)
Found out about this film when doing a quick internet search on William Hopper (Paul Drake, the private investigator on Perry Mason). When I saw it also had Craig Stevens (Peter Gunn) and Keye Luke in the credits, I had to get a copy. Unfortunately, Warner Bros has not seen fit to release it on video yet.