Callan is assigned to disrupt a romance between a government worker and a suspected spy. Reluctantly he delves into his bag of dirty tricks.

Callan helps a former agent out of a blackmailing business.

Callan and Cross are assigned to protect a woman whom Callan becomes involved with.

When Cross kills an innocent bystander it's up to Callan to cover for him, but even he cannot decide if it was an accident or murder.

The new Hunter cannot decide if Callan is to return to the Section or not.

A freelance German mercenary organisation who specialise in eliminating foreign security sections have their sights set on the Section.

Security wants a retired brigadier of the British army to be stopped from accepting a job offer from a sultan, deadly force is requested.

Hunter, head of the Section, requires the services of his best operative, David Callan. Callan had been 'retired' from the service due to his growing conscience, disrespect for orders, and concerns about the people he was ordered to eliminate. Callan now working as a bookkeeper, a job he despises, is offered to be reinstated into the Section if he kills Schneider, an international arms dealer.

Under threat of being placed in a red file, Callan is coerced into helping the Section hand over an ex-SS officer, Strauss, to the Israelis.

Callan must stop an old friend, Clarke, from going back to Africa, where he was training mercenaries, else Hunter will have Clarke killed.

The Section's new Hunter has Callan pulled from the field.

Callan apparently turns renegade. A ruse to trap the head of a ‘pipeline' for smuggling foreign agents and defectors out of the country.