Ken Williams befriended a retired highway patrol officer named Jim Walls and asked him to produce an adventure series based on a police theme. Walls proceeded to create "Police Quest: In Pursuit of the Death Angel", which was released in 1987. Several sequels followed, and the series was touted for adherence to police protocol (relevant parts of which were explained in the games' manuals), and presenting some real-life situations encountered by Walls during his career as an officer.