This grim historical drama from director Martin Ritt was loosely based on real-life events.
Richard Harris stars as James McParlan, an operative for the Pinkerton Detective Agency in 1876. The Pinkertons have been hired by a major coal company to infiltrate and expose an underground terrorist organization, the Molly Maguires, operating within the impoverished mining communities of Pennsylvania.
As most of the miners are Irish, the recently emigrated McParlan is selected to pose as a new worker just arrived in the area. He quickly wins the trust and loyalty of the local terrorist leader, Jack Kehoe (Sean Connery), as well as the affection of his landlord's beautiful daughter, Mary Raines (Samantha Eggar).
As it becomes clear that the group he's supposed to betray is protesting truly wretched working conditions, the lawman's loyalties become divided between the law and his fellow countrymen. The Molly Maguires (1970) was Oscar nominated for Best Art and Set Direction.