A cat-and-mouse game between the police and the Mafia thrives in Boston’s underworld. When young cop Billy goes undercover in a gang led by Frank, he simultaneously infiltrates a police squad led by Costello. At the same time, Costello infiltrates his sidekick into the police department. A dangerous game of two bottoms begins, where everyone is in danger of being exposed. The complexity of the situation is compounded when both double agents begin to suspect each other. As the tension builds, the solution to the mystery becomes increasingly unpredictable.