A television movie pilot airing in March 1972 introduces five new cadets at a police academy in an unnamed Southern California city. These rookies come from diverse backgrounds, including military service, college, and social work. The success of this pilot leads to a weekly series that follows three of these officers through their early years on the force. The show centers on Mike Danko, a former Marine adjusting to civilian life; Willie Gillis, a recent college graduate; and Terry Webster, who joined the department through a minority recruitment program. Their direct supervisor is Lieutenant Ed Ryker, a veteran officer who serves as their mentor and guide in the field. Mike Danko is married to Jill, a registered nurse, and their home life is regularly featured as part of the storyline.

The setting is the fictional Southern California Police Department (SCPD), though the series was filmed in and around Los Angeles. Each episode dramatizes police cases and activities, intertwining the officers professional duties with their personal lives. The show attempts to humanize police characters during an era of public controversy and negative feelings toward law enforcement, presenting the struggles of younger officers who are often Vietnam-era veterans or college graduates. After the second season, actor Michael Ontkean leaves the series, and his character Officer Willie Gillis is replaced by a new rookie, Officer Chris Owens. During the third season, a two-part episode serves as the pilot for a spin-off series focusing on a special weapons and tactics team. The series runs for four seasons, with the final episode airing in March 1976.