This QM (Quinn Martin) show follows the cases of Lt. Mike Stone and his young partner Steve Keller as they use modern police methods to track down criminals, against the backdrop of the Bay Area. Mike was a 23-year veteran of the force, a widower, assigned to the Bureau of Inspectors Division of the San Francisco Police Dept.Steve, a smart, 28-year-old college-educated man who rose from assistant inspector to inspector during his tenure on the show. In 1976 he left ("to enter teaching") and was replaced by athletic Dan Robbins. Mike's coed daughter was seen occasionally during the early years, but later the emphasis was shifted to the cases, rather than the homelives of the principals. The series was based on characters from the novel Poor, Poor Ophelia, by Carolyn Weston.