The Whistle Blower

Frank Jones (Michael Caine) is a war veteran whose son Bob (Nigel Havers) worked as a Russian translator for British intelligence during the Cold War. When Bob turns up dead, Frank starts asking questions and finds that everyone who might answer them has a reason to stay quiet. Simon Langton follows him through that wall of polite deception, and Frank keeps pushing at it because the one person he owed protection to is gone.