Having set his sights on infiltrating the dangerous American-Irish gang of local mob boss Frank Costello, young police officer Billy Costigan puts his morals and sanity to the test. Meanwhile, as Billy gains Costello's trust, Massachusetts State Police detective Colin Sullivan becomes Costello's paid informant. As a result, both men immerse themselves in their secret double lives, trying to gather valuable information about each side's plans and operations. However, there is a mole in their midst. Now the impostors are between a rock and a hard place, trapped in a volatile situation that can easily blow their cover. Can the stealthy infiltrators survive the white-knuckle game of betrayal and save their skin?—Nick Riganas