The menace of Harold Pinter's script is marvellously sustained by director Michael Anderson in this espionage thriller, with George Segal giving one of his finest performances as the secret agent investigating a neo-Nazi movement in 1960s Berlin. Alec Guinness and Max von Sydow excel as, respectively, the British spy chief and his evil Nazi counterpart, and, for once, a woman (Senta Berger) plays a formidable part in an ambiguous role, the true nature of which is only revealed in the final shots.

After two British Secret Intelligence Service agents are murdered at the hands of a cryptic neo-Nazi group known as Phoenix, the suave agent Quiller is sent to Berlin to investigate.