David Callan is a senior operative in a shadowy, secret branch of the British secret services known as The Section. He's an ex-convict, ex-army, something of a loner and perhaps something of a misfit in a line of work where most of his colleagues are upper class career spies - the faintly psychopathic Toby Meres; the brash, callous James Cross.
But as his section chief, codenamed Hunter, knows: Callan is the most valuable of all of them. Clever, resourceful, hard as nails and impeccably thorough. A dead shot with the cold nerve to kill. He gets the red files: high risk operations, high priority targets, assassinations.
To assist him on some of his operations Callan pays an associate whom he met in prison, known as Lonely. Lonely knows nothing of Callan's real line of work, assuming him to be part of the criminal underworld. He's a shifty, nervous and rather malodorous character. But he knows better than to ask questions, and he's brilliant at following people and picking locks.
Callan doesn't have the glamorous lifestyle of a James Bond; no fast cars, no casinos. He lives in a rather ordinary flat somewhere in South London. The offices of the Section are a sort of dingy basement, with old metal filing cabinets and an annexed shooting range.
Callan's trouble is his conscience. He sometimes loathes the brutal work of the Section, in which people are marked for death at a stroke of a pen or destroyed by powerful hallucinogenic drugs in interrogation. He has a strong anti-authoritarian streak.
But he knows that his dirty work in the Section is the one thing that he does brilliantly well.
And besides, if he did leave, he might just find himself in a red file of his own.