The Wyoming Wildcat: Cowboy Phil Stone gets a job as foreman on a ranch owned by pretty young Isabel Hastings. He discovers that ruthless rancher Jeff Kopp has a claim on Isabel's ranch, and that if she dies unmarried before she turns 21, Kopp will get her ranch. When Isabel turns down a marriage proposal by Kopp's son Rudy, Kopp decides to kill her and get the ranch for himself, and hires a notorious killer, "Cyclops", to do the deed.