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.

Two CIA agents request the help of Hunter's Section in killing a Chinese agent, who has been trading in nuclear secrets. But his real mission in England is to kill Hunter.

Callan is lured into going to Berlin, where Hunter wants to use him as a sacrificial lamb to facilitate the planting of a British mole.

Hunter wants Callan to stop a blackmailing Lord from selling the negatives used in the blackmail to all and sundry.

When somebody beats Lonely up, and Callan finds out who it was he turns the table on Hunter.

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

Callan must prove that a young biochemist is not giving information to the East.

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

Callan must use the wife of a rocket scientist as bait to lure the same scientist to Britain.

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

After Hunter's death Meres and Calln must fetch the new Hunter from East Germany.

Callan must retrieve a microfilm from a spying medium.

Calln must find everything out about the past of an influential politician.

The French O.A.S. carry an internal war into England. Callan and Meres must sort out the mess.

Callan and Meres must catch the controller of a ring of spies before he can leave the country with the information the ring has gathered.

Callan and Meres must secure the safe of a ship that was sunk during World War Two. It contains a list of Third Reich collaborateurs and puppets. A survivor of the ship tries to stop them.

Callan must stop fashist agitators from killing the Chinese Ambassador.

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

Callan brings confusion into a Russian spy network.

Callan in brainwashed into believing that Hunter is the leak in the Section and that he has also killed Lonely and framed Callan for murder. In his drugged state Callan kills Hunter and is shot down by Meres.

Callan is dead. Or so the KGB would have you think.

Lonely is used as bait to retrieve Callan from the KGB.

Callan has become the new Hunter. And his first job is to retrieve a list of British undercover agents.

Callan orders Cross to terrorise an innocent Russian family for political reasons.

Callan looses his position as Hunter when he goes after the assassin who killed Cross.

The old Hunter returns and Callan tries to get away.

Callan tries to quit the Section when a girl he is seeing takes a dislike to his job.

Lonely becomes the unlucky witness to a mob hit.

Callan tracks down Richmond who is trying to leave Britain.

Callan and Lonley break into a courier's house to find out how he's operating.

Callan substitutes himself for an assassin in order to prevent an assassination.

Callan debriefs a top enemy defector.

Richmond, a top enemy defector, reveals his true purpose.