This 1955 period piece recreates the notorious events surrounding the murder of architect Stanford White by Harry K. Thaw. This famous homicide, later immortalized in E.L. Doctorow's novel Ragtime, transpired on the Winter Garden roof in full view of countless theater patrons. Joan Collins stars as Evelyn Nesbit Thaw, a single showgirl who grows enamored with the married White (Ray Milland). He takes her to his posh Manhattan loft and enjoys a dalliance with her that includes pushing her on the red velvet swing of the title. Later, Evelyn gets courted by Harry Thaw (Farley Granger, who - after whisking her off to Europe and wheedling her into marriage - suddenly turns out to be a complete nutcase, driven around the bend by violent jealousy and rage. He grows incensed at the memory of her affair with White, and decides to to take drastic action by shooting the architect; in the wake of the murder, Thaw builds a fantastic legal defense that permanently alters his fate. Few of the facts in this tawdry soaper are true to history, because, as Bosley Crowther famously pointed out in his Times review, Evelyn Nesbit Thaw was still alive at the time of this production and the filmmakers probably feared a libel suit.
by Hal Erickson synopsis