Overview
The Key is a 1934 American Pre-Code film directed by Michael Curtiz. It was re-issued as High Peril (pre-release title Sue of Fury) in 1960.
The story, concerning a love triangle, is set during the Irish War of Independence.
Plot
Captain Bill Tennant (William Powell) is a British officer stationed in Dublin in 1920. Tennant had a month long tryst with Norah, the wife of his friend, British intelligence officer Captain Andrew Kerr, three years ago before Norah and Andy met.
Tennant's first assignment is to capture a notorious Sinn Féin member, Peadar Conlan. His first attempt is a failure, and Kerr is ordered to relieve Tennant overnight. Norah is frightened by his assignment and begs her husband not to go. After Kerr leaves, we see a flashback to when Tennant and Norah were involved, several years before.
From Wikipedia (CC BY-SA 4.0).