David Callan is the security service's main agent/killer.

David Callan is the top agent/assassin for the Security Service (British counterintelligence), but he is an embittered man who performs his duties "for Queen and country" under duress. This bleak, "Spy who Came in from the Cold"-style espionage drama concentrates on the seamy underside of covert operations: assassinations, blackmail and dirty dealing.—Marg Baskin <[email protected]>