 After three women are murdered following the placement of ads with "Lonely Hearts" clubs, Dan Mathews and Officers Larrabee and Simpson set a trap by having policewoman Faye Nelson place a similar ad. A man calling himself "Herman Warren" answers the ad and Faye finds his manner somewhat menacing, but he leaves without incident. Despite the failed effort, Dan directs Officers Larrabee and Simpson to tail the suspect. When he unexpectedly turns onto a side road, Dan and his officers return quickly to Faye s location and find themselves engaged in a gun battle. They subsequently learn that the entire killing spree was motivated by the suspect s psychotic determination to find and kill his ex-wife "Judy".