- Country: UK
- Genres: Drama
- Release: 1964-08-19
- Director: Montgomery Tully
- Writers: Maurice J. Wilson , Montgomery Tully , Gerald Anstruther , Paul White
- Language: English
- Stars: Stephen Murray , June Thorburn , Alan Wheatley , John Carson , John Bown , Jack Watson , Ernest Clark , Peter Gilmore , Marne Maitland (1920–1991) , Ellen Pollock
- Runtime: 70 min
- Awards: N/A
- AKA: Master Spy , X 21 spionaggio atomico (Italy) , Master Spy (United Kingdom) , Checkmate (United Kingdom)
- Plot: A Russian scientist working for the British is suspected of being a "plant", sent to monitor nuclear secrets on behalf of the communists.
- IMDB:tt0058334
Master Spy Cast · · · ALL
Montgomery Tully
Director
Stephen Murray
Boris Turganev
June Thorburn
Leila
Alan Wheatley
Paul Skelton
John Carson
Richard Colman
John Bown
John Baxter