Mary Alice Siem was a student at the University of California, Berkeley when she became involved in 1973 with a prisoner outreach program at Vacaville Prison. She became the girlfriend of Thero Wheeler, an inmate who escaped in August 1973. He was a founding member of the Symbionese Liberation Army (SLA), an extremist group based in Oakland that was classified as terrorist by law enforcement. It was known for murders, armed robberies and the kidnapping of heiress Patty Hearst after Wheeler and Siem left the group in October 1973.