You're Out of Luck (1941)

Frankie O'Reilly, a hotel elevator-operator, and his pal, Jeff, are working at a classy hotel where a guest, Hal Bayor, is murdered, and Jeff is an unwitting witness. Frankie's older brother, Tom , is the police detective assigned to the case. Frankie decides to crack the case on his own and, since Jeff witnessed the killing, Frankie insists that Jeff accompany him on a tour of the city's nightclubs and gambling dens in order to find the killers...who are not in the mood to be found.