This is a minor studio production which has become a B film legend. Nina Foch takes a job as a secretary to a family of nutcases who abduct her and lock her up on a remote estate in Cornwall (shot in California). They need her to stand in for the woman who was murdered by her psychopathic husband (George Macready).
They parade their prisoner as the dead wife for the benefit of local witnesses, claiming her protests are part of her psychosis. OK, it's a crazy story, though no more than many other golden age mysteries. It succeeds because director Joe Lewis stages it so well. No screen time is wasted, and there's a brilliant noir house-of-shadows.
Foch is plausible in the difficult title role, but the crazy kidnappers make a bigger impression. May Whitty is the eccentric but ruthlessly pragmatic mother of the simple-minded Macready. He is splendidly menacing as the killer who relishes their plans for the stand-in, while also enjoying having her as his wife, for a while.
It is set in England where, in the minds of Hollywood producers, these things happen. Like Gaslight. Critics like to flag up the doomed males of film noir as a key postwar motif, exploited by predatory females. But there are many women like Julia too; lonely, vulnerable and manipulated. This is among the most typical and successful of these woman-in-peril films.