Convict Gilbert – Gordon Sugden
Convict Crosby – Harry Chapman
Warder Mullins – Laurie Cook
Warder MacBain – George Mitchell
Detective Constable Grummett – Jack Whitaker
Clara Grummett (his wife) – Margaret Holbrey
Alexander Grummett (their son) – Andrew Bailey
Evadne Docherty – Mary Newton
Headmaster Horace Winston Allardyce – John Burgess