Callan Season 2 Episode 15 Death of a Hunter

Hunter believes that there is a traitor in the Department, and the only operative whom he trusts is Callan. Callan is therefore commissioned to watch an opposition agent known as Striker to see whom he contacts. Callan gets Lonely to break into Striker's flat to look for a cipher pad, and Lonely finds Striker's dead body in the flat.

In the meantime, Meres receives a phone call purporting to be from Hunter. Meres is tricked by the opposition who take him to Striker's flat where he arrests Callan on charges of Espionage.

Callan is spirited away by the enemy agents and is brainwashed into believing that the enemy agent in the Department is Hunter himself. He is brainwashed for a week, then released. He immediately heads for the Department and shoots and kills Hunter who is working at his desk. Callan is then shot and wounded by Meres and only then does Callan realise that he has been tricked.