Here Come the Girls (1953)

Stanley Snodgrass, perhaps Broadway's clumsiest (if not oldest and most out-of-tune) chorus boy, finds himself unceremoniously ousted from yet another show, but when an infamous slasher starts threatening the show's leads, Stanley is brought back as the headliner, unaware that the police are using him as bait. Even with Detective Logan secretly posing as Stanley's valet, producer Harry Fraser fears Jack the Slasher may not put in an appearance soon enough to prevent Stanley from murdering his show.