A police lieutenant refuses to drop a murder investigation written off by his superiors as a suicide, eventually giving up his job to pursue the mysterious killer of a popular composer with a string of cast-off girlfriends. A musical clue (the nocturne of the title) finally cracks open the case.
|Lieutenant Joe Warne||George Raft|
|Frances Ransom||Lynn Bari|
|Carol Page||Virginia Huston|
|Edwin L Marin|