Mark's date is found murdered in Golden Gate Park, and he is determined to catch the man responsible, with or without Ironside's help. When he decides to take the law into his own hands, however, he finds himself under arrest for the murder of the chief suspect.

An old woman whose handbag has been snatched asks Ironside to take her case. Moved by his friendship with her late husband, he agrees, and finds a lonely old woman reaching out for somebody to share her long days.

A string of murders is committed, and in each case the victim has a numbered disk in their possession. After number four is found dead, it transpires that the Commissioner is the owner of disk number six; and the Chief disguises himself as number five - an irascible artist to whom he bears a striking resemblance - in order to keep him alive.

While Fran, Mark and Ed are at a night club, a psychic sees details of a recent fire. When the Chief becomes interested, he visits the psychic to try to see more, and discovers that he has been pursuing an arsonist for some time, unable to convince the police that his visions are for real.