An old friend of the Chief's tries to commit suicide, after local gossip and the media both blame her for the murder of her husband. Ironside is determined to find out the truth about the death, even if it means proving that his friend really is guilty.

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.

Ed goes to LA to fetch a prisoner, but when confronted by a pair of hostile beat cops after a mugging, he loses his cool and ends up in the County Jail. Caught up in a blatantly unfair system, he begins to doubt his own integrity as a representative of a law that is clearly failing so many people; and refuses to allow the Chief to bail him out.

A girl thought to have died years previously turns up at the home of her mother just as her brother is found murdered. Clearly somebody is trying to kill the family off, but is it connected to the girl, and is she really who she says she is?

A British police inspector visits San Francisco for a conference, and whilst there assists his old friend Chief Ironside with an awkward investigation. It soon appears, however, that he knows more about the case than he should do, and that his involvement may have something to do with his deteriorating state of health.