To Catch a Thief (1955) ending / spoiler
John Robie agrees to attempt to cat The Cat in action at the costume ball with Francie's help. While at the ball, he spies The Cat running across the roof of the mansion. Robie gives chase, a tussle ensues, and Robie pulls off The Cat's black mask to reveal...Danielle, the daughter of the Bertami sommelier and an acquaintance of Robie's. He makes her fess up to the police then and there. He and Francie then live happily every after.
Submitted by Celeste Harmer