Nice Guys Finish Last - S2.E10

Police Lieutenant Dave Harker, a friend of Don's, is bitter after being denied a promotion to Captain, and decides to frame nightclub owner and high school rival Nick Culley, whom he blames for the pass over, for murder. Harker in turn is being blackmailed by a man who knows the truth. Devlin goes undercover as a rookie cop to keep an eye on Harker.