Hamilton

A Bow Street Runner summons Captain Gabriel Lacey to a Berkeley Square ballroom where a young dandy was stabbed to death during a society ball. The prime suspect: Lacey's former commander, Colonel Brandon. Instead of denying the charges, Colonel Brandon allows himself to be arrested and claims, to Lacey's shock, that the lady he'd stayed protectively near at the ball is his mistress. Lacey realizes that he is the only person not convinced of Brandon's guilt - all present, including Brandon's wife, believe that Brandon committed the murder.