Aging Boston gunrunner Eddie Coyle (Robert Mitchum) is looking at several years of jail time for a hold-up if he doesn't funnel information to Dave Foley (Richard Jordan), an ATF agent. Eddie buys some guns from another gunrunner, Jackie Brown (Steven Keats), then gives him up to Foley, but the agent isn't satisfied. Conflicted, Eddie decides to also give up the gang of bank robbers he's been supplying, only to find that Foley already knows about them, and the mob believes Eddie snitched.