The Molly Maguires (1970) on Netflix

In 1876 Pennsylvania, a group of Irish immigrant coal miners begin to retaliate against the cruelty of their work environment.

Life is rough in the coal mines of 1876 Pennsylvania. A secret group of Irish immigrant miners known as the Molly Maguires fights against the cruelty of the mining company with sabotage and murder. A detective, also an Irish immigrant, is hired to infiltrate the group and report on its members. But on which side do his sympathies lie?

—John Oswalt <jao@jao.com>

A terrorist group known as the Molly Maguires has been sabotaging a coal mine in Pennsylvania where they work. Detective McParlan as McKenna must infiltrate the group led by John Kehoe. Throughout the film McParlan's allegiances are tested. Will he side with the Maguires and become a true member, or keep his mission in mind and bring an end to the group?

—FMJ_Joker