Frank Cannon was a detective with the Los Angeles police department. However, he resigned after the deaths of his wife and son in a car accident and later became a private detective. The cause of death of Cannon's wife and child is not clear, although it is mentioned that Cannon's wife and child were killed in an explosion caused by a bomb meant for Cannon.

Although the noticeably overweight Frank Cannon has expensive tastes, especially in food and cars (his primary vehicle is a silver '71 Lincoln Continental Mark III), he also feels there is a need for someone to help people who have little or no money. For this reason, he charges his more affluent clients hefty fees so he can aid the less affluent.

Frank currently resides in the penthouse of the Sunset Tower. His home includes a shooting gallery and full bar.