CI5 and their agents find themselves under attack from a vendetta of bombings and assassination attempts. Bodie and Doyle are on a chase to find out who the perpetrators are before they end up as the next victims.

Cowley is offered the name of a highly-placed double agent from an old colleague - who in return wants to be guaranteed protection with CI5. This leads to the start of a dangerous stand-off between the two, using Bodie and Doyle as the pawns.

A spy is extradited to Britain with an attempt to keep his arrival top-secret. However, the Bulgarians from Batak's homeland who sent him appear to be trying to make his movements as public as possible. When he is eventually murdered, CI5 suspect his music student daughter of poisoning him.

Years after a man's wife died and his child left brain-damaged following a series of blunders at the hospital they were treated at, he returns to finally seek revenge by systematically assassinating each of the same hospital's medical staff one-by-one.

A dummy run that has been staged for the visit of a Middle Eastern official is found to have been recorded by a foreign student, subsequently leading CI5 to suspect a security leak.

An attempt to start up a street war is launched by a gangland breakaway opposition group, but their leader appears to have an ulterior motive in his actions.

Bodie and Doyle are shocked to discover that Cowley appears to be selling nerve gas to a group of East Germans in order to line his own pockets, and are assigned by his rival Plumb to track their boss's every move.