The plot turns upon a lost diamond of great price, but mostly the film is a string of lively, unrelated escapades.

With mood and action the keynote of the John Houseman production, the direction by Fritz Lang plays both hard, developing considerable movement in several rugged action sequences without neglecting suspense.

A boy and a rakish smuggler search for a legendary lost diamond in a wonderfully stylised version of 19th century Cornwall.

[One] reason why Moonfleet makes for a poor children’ s film is because of how terribly boring it is.