 Siringo infiltrated the Gem Miners' Union, and decided that the leadership was in the hands of anarchists such as George Pettibone.After 1 year and 2 months, which included the Coeur d'Alene, Idaho labor strike of 1892, Siringo's undercover work and testimony helped convict 18 union leaders.Siringo married Lillie Thomas in 1893, and their son William Lee Roy was born in 1896.