Stage Fright (1950)

Synopsis
Stage Fright toys with our notions of the dividing line between reality and artifice by being set in the London theatre world. On the lam from the police, Richard Todd takes refuge in the home of his former girlfriend, RADA student Jane Wyman. Todd has been spotted fleeing the scene of a murder, but he insists that he's innocent. Wyman believes his story, but knows that the police won't, so she decides to play detective herself. She also plays several other roles in a variety of disguises so as to escape the notice of genuine detective Michael Wilding. Top-billed Marlene Dietrich plays a Dietrich-like chanteuse whom Wyman pigeonholes as the real murderer. ~ Hal Erickson, All Movie Guide