During the Korean War, Italian nurse Virna Lisi falls in love with two American fliers, Tony Curtis and George C. Scott. Lisi marries Curtis after he convinces her that Scott has been killed in a plane crash. She soon discovers Scott is alive, but remains happily married to Curtis until Scott re-enters their lives 14 years later.

This Universal programmer was based on a Collier's Magazine story by journalist Quentin Reynolds. This story in turn was ostensibly based on a true incident, in which a gangster "returned from the dead" to save an innocent young man from the electric chair. The nurse of the film's title is Katharine McDonald, who falls in love with her prizefighter-patient Lee Burke as he recovers from a beating received in a fixed prizefight. Katharine must fend off the advances of criminal attorney John Dodge, another patient who also loves her and becomes jealous of Lee. But when Lee is framed for the murder of his disgruntled manager, Slice, by a henchman of the fight-fix leader, Joe Largo, Dodge takes on his defense and works with Katherine to discover the real killer. Convicted and sentenced to death, Burke is about to walk the "last mile", as Katharine encourages mortally wounded Largo to a deathbed confession.