The Blue Dahlia
A frequently used variation on the theme involved an average person who is suddenly forced to turn ad hoc detective in order to solve the murder of a friend or clear their own name. Prime examples include Jack Oakie in "Super-Sleuth" (1937), Ella Raines in "Phantom Lady" (1944), Lucille Ball in both "The Dark Corner" (1946) and "Lured" (1947), Alan Ladd in the aforementioned "The Blue Dahlia" as well as "Calcutta" (1947), George Raft in "Johnny Angel" (1945), June Vincent and Dan Duryea in "Black Angel" (1946), Humphrey Bogart in "Dead Reckoning" (1947), and Dick Powell in "Cry Danger" (1951).