This film documents the historical two-year infiltration of an informant, James McParlan / McKenna, into a group of disgruntled Irish coal miners in the 1870s who had turned to terrorism in combating horrible working conditions. The infamous Molly Maguires, a name originating from cut throats on the island of Eire who fought landowners, often dressing up as women, hid within the Ancient Order of Hibernians, the largest fraternal organization in North America at this time. Sean Connery plays the famous John "Black Jack" Kehoe, whose historical role in the Molly's is emphasized in the film -- celebrated or denigrated, depending on audience judgment. The role of race is shown, if not toned down, with accuracy regarding Irish, Welsh, and English grouped within the social / political / economic hierarchy of the times (Irish being the most discriminated against). The film shows the fight against the unjust working conditions Irish Catholic adults and children alike suffered under English, Welsh, even fellow Irish (Protestant) capital owners and supervisors. With all the violence, threats, explosives, and murder which still echo across the hills to the ears of the current Pennsylvanian occupants, the film is a unique glimpse into the earliest of labor fights leading to child labor laws, minimum wage, and the search for a supportable wage. In the end, three men, Kehoe among them, are sent to the gallows.