Callan is a brooding, conscience-stricken assassin for a shadowy British intelligence service so secret it doesn't have a name. With the Cold War grinding on, agents from the East and West engage in elaborate deceptions, both sides seeking temporary advantage in an endless struggle. Callan's sharp eyes, steely will, and steady hand with a gun make him a valuable asset to his superior, Hunter. In a world where men and women serve only as means to another's end, Callan fully understands the consequences of failure, seizing each assignment as one more chance to survive.