http://www.san.beck.org/MM/1934/Key.html
Based on a play by R. Gore-Brown and J. L. Hardy, a British officer sacrifices himself to save the husband of his old flame amidst the British-Irish conflict in Dublin.
In 1920 Dublin the British army imposes a midnight to 5 curfew while they search for Sinn Fein leader Peadar Conlan (Donald Crisp). Andy Kerr (Colin Clive) tells his wife Norah (Edna Best) he killed Kirby. British Captain Tennant (William Powell) arrives, reports to General Furlong (Halliwell Hobbes), and is given an apartment in the same building as his old friends Andy and Norah. He explains to Norah that he left her three years ago because he would not be a good husband. She says she is married and happy. Tennant puts on an overcoat and mingles with the Irish, meeting liaison O'Duffy (J. M. Kerrigan). The general orders Tennant to find Conlan; but before his men can search the Key, there is a shoot-out.
Tennant comes to take Kerr on duty; but Norah begs him not to go because she is afraid. Kerr goes. Norah tells Tennant they don't love each other any more; but they remember when they were happy together. Looking for Conlan, Kerr shoots one of his men and captures Conlan. He tells Norah he will get 1,000 pounds, and they can go on vacation. Then he finds Tennant there. Norah asks Tennant to leave and tells Andy that he is the "someone else." Kerr goes out, and Norah has Tennant go after him. The British army sentences Conlan to hang. Kerr goes to a bar and is abducted by Sinn Fein. Tennant tells Norah he loves her more than his freedom; but she says she loves Andy.
O'Duffy tells the general he is opposed to all killing, that Kerr was taken alive, and that they will trade him for Conlan. Norah asks the general to save her husband; but he says this is an army. Tennant gets in to see O'Duffy but cannot make a bargain for Kerr. So Tennant breaks into the general's desk and forges a release order for Conlan. Kerr is let go because Conlan was released. Amid Irish celebrations the general orders a search for Conlan. Lt. Merriman tells the general it was Tennant who forged the order, meaning the end of his career. Tennant tells Kerr that Norah was in love with a memory but now she realizes she loves her husband. Tennant turns himself in and faces at least three years in prison.
The historical British-Irish conflict provides a somewhat educational context for this romantic melodrama in which a romantic bachelor saves his friend by gallantly breaking army rules. Meanwhile the wife learns the difference between a romantic affair and a loving marriage.