A British officer stationed in Ireland falls for the wife of an intelligence man.

In 1920, in response to Irish demands for home rule, the British impose martial law on their neighboring nation. Andrew Kerr is a member of the "Black and Tans," a British army unit sent to maintain order in Ireland. He is troubled by his position, as his mother was Irish, but his wife Norah consoles him, saying that this is politics, not war. Bill Tennant, an old army friend of Andrew, is sent to Dublin and rents the flat below the Kerrs's. When Andrew invites him up for tea, Bill realizes that Norah is a woman he was in love with years before but left because he did not want to be tied down. Upset by his meeting with Norah, Bill has a drink in a pub. When he spots Bill's uniform underneath his overcoat, O'Duffy, a go-between, gives him a password to use if he should ever want to help the Irish. That evening, Andrew is assigned to search the dock area for Peadar Conlan, one of the Irish leaders, who is a fugitive from justice. Norah begs him not to leave, but he cannot shirk his duty. While he is gone, Bill and Norah rekindle their romance. When Andrew returns after capturing Conlan, he finds them together, at which point Norah tells him that she knew Bill before and still loves him. Andrew runs out into the streets, where he is recognized as the man who captured Conlan and is held hostage for Conlan's release. Norah, having realized that she really loves Andrew, tells Bill that he is a romantic dreamer. When the British refuse to trade Andrew for Conlan, Bill uses the password O'Duffy gave him to negotiate for Andrew's freedom. He forges a release for Conlan. Bill is arrested, but he has reunited Norah and Andrew.