A female version of the man in the iron mask. In this version the mask is put on a princess (patricia medina) rather than a prince as in the original book by Alexander Dumas.

During questioning by the police, a railway worker falls to his death from the multi-story police HQ. The government says it was an accident but there is a public outcry. The Superintendant and Inspector responsible are awaiting the arrival of an Investigating Judge but get more than they bargained for when a lunatic escapes and impersonates him.