Lured to a prison with a promise of information, the Chief and Mark are taken hostage by three convicts desperate to escape. Together they plot to undermine the escape attempt by turning the situation to their own advantage.

The Chief begins to receive strange phone calls, warning him of a murder to be committed somewhere in San Francisco, apparently in the interests of justice. With very little to go on and virtually nothing to help him identify his mysterious caller, Ironside eventually traces the case back to a policeman, thrown out of the force fifteen years earlier.

A military-issue fragmentation grenade is used in an attack on two Vietnam veterans, one of whom - a friend of Mark's - is killed. When it transpires that another of the pair's old unit has come under similar attack, the Chief sets out to trap the killer, using Ed in a cunning disguise as bait.

A series of murders appear to be connected to an old friend of the Chief's, an ageing woman from San Francisco's old rich set; and when the murders are linked to her debutante's ball and she appears to be exhibiting signs of deteriorating mental health, the odds look stacked against her. As always, though, the Chief looks elsewhere to find the truth.