"The Claydon Treasure Mystery" stars reliable John Stuart as an engineer (Peter Kerrigan) interested in solving mysteries, who becomes involved in investigating murders at Marsh Manor, home of the wealthy Claydon family. Plenty of suspects to choose from, Kerrigan believes that the murders may be connected to hidden treasure on the estate.
| Actor | Role |
|---|---|
 John StuartPeter Kerrigan | Peter Kerrigan |
 Garry MarshSir George Ilford | Sir George Ilford |
| AAnnie EsmondLady Caroline Claydon | Lady Caroline Claydon |
 Campbell GullanTollemache | Tollemache |
 Evelyn AnkersRosemary Shackleford | Rosemary Shackleford |
 Aubrey MallalieuLord Claydon | Lord Claydon |
 Finlay CurrieRubin | Rubin |
 Joss AmblerInspector Fleming | Inspector Fleming |
| VVernon HarrisRhodes - the Butler | Rhodes - the Butler |
| RRoy RussellNot listed | Not listed |
| EErnest BorrowNot listed | Not listed |
| VValentine DunnMargaret McGregor - the Maid | Margaret McGregor - the Maid |
 Ian FlemingDr. Cleveland - Coroner | Dr. Cleveland - Coroner |
 Wilfrid Hyde-WhiteHolmes | Holmes |
 John LaurieWilson - the Valet | Wilson - the Valet |
| BBen WilliamsGamekeeper | Gamekeeper |
 Donald WolfitExecutive | Executive |
| RRichard ParrySgt. Midgley | Sgt. Midgley |