Wiseguy - Season 3 Episode 14

Steelgrave's former accountant, Sid Royce, is suffering in the Witness Protection life Frank assigned him. When his wife leaves, he snaps and decides to get revenge against Frank for destroying his life. Jenny agrees to have dinner with Frank, then invites him back home. Their romantic evening is destroyed when Sid pulls a gun on them. Jenny talks Sid into letting Frank go by convincing him she's his missing wife. Frank kills Sid in front of Jenny, ending whatever chance they might have had at reconciling. (source: http://www.plasticcow.com/wiseguy)