Between Midnight and Dawn (1950)

"THE STORY OF PROWL CAR 13...BASED ON THE POLICE FILES OF A GREAT CITY!"

Rocky and Dan, war buddies, are prowl car cops on night duty. Dan is a cynic who views all lawbreakers as scum; Rocky feels more lenient. Both are attracted to the radio voice of communicator Kate Mallory; but in person, Kate proves reluctant to get involved with men who just might stop a bullet. By lucky chance, Rocky and Dan cause big trouble for murderous racketeer Ritchie Garris; but when he swears vengeance, Kate's fears may prove justified.