David Callan is the top agent/assassin(retired) for the S.I.S. (British counter intelligence), but he is an embittered man who performed his duties under duress. Now pressured into returning to duty Callan reluctantly but efficiently performs the tasks given to him. This espionage drama concentrates on the seamy underside of covert operations: assassinations, blackmail and dirty dealing.
Aired: 1972 - 1981