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

When Los Angeles private detective, Harry Moseby is hired by a client to find her runaway teenage daughter, he stumbles upon a case of murder and artifact smuggling.