Catherine Willows (previously Flynn) is a fictional character from the CBS crime drama , portrayed by Marg Helgenberger. She made her first screen appearance in the show's pilot, broadcast on October 6, 2000. Catherine was a crime scene investigator and forensic scientist for Clark County, Nevada, until she accepted a job with the FBI. Helgenberger announced her departure in 2011, with Catherine making her last appearance in the episode "", which aired on January 25, 2012. She later returned in the show's broadcast on October 23, 2013. Helgenberger received several award nominations for her portrayal of Catherine, including two Primetime Emmy Award nominations and two Golden Globe Award nominations.