1935’s The 39 Steps tells the story of Richard Hannay, a man who becomes tangled up in an international espionage organization—the eponymous “39 Steps”—that are attempting to steal British military secrets. The movie was one of director Alfred Hitchcock’s earliest non-silent movies and remains one of his most popular masterpieces.

Hitchcock, as well as being one of cinema’s best-known directors, was as well known for his idiosyncratic (and often somewhat questionable) behavior on and off set as he was for the quality of his movies—and The 39 Steps was no different.

His quest for perfectionism, and his love of maliciously taunting his leading actors and actresses along the way, came to a head when filming a scene in The 39 Steps in which the character Pamela (played by Madeleine Carroll) is handcuffed to Hannay (Robert Donat).

Hitchcock had his two stars genuinely handcuffed together and kept them as such for much of the remainder of the day. By the time filming finally wrapped that night, Carroll’s wrists were red raw and bleeding, and were covered in welts and blisters where the uncomfortable metal cuffs had chafed the skin underneath.

Despite her obvious discomfort, Hitchcock still couldn’t help himself from pulling a malicious prank, and for several hours after filming pretended to have lost the key to the handcuffs. Finally, he relented and released his two stars from their torturous confinement.