Let's Kill Uncle (1966)

A 12-year-old orphan who has just inherited a fortune is trapped on an island with his uncle, a former British intelligence commander who intends to kill him. A young girl is the boy's only ally against the sarcastic uncle, who uses hypnotism, a pool of sharks, fire, and poisonous mushrooms as weapons.

Directed by: William Castle

Starring: Nigel Green, Mary Badham, Pat Cardi, Robert Pickering, Linda Lawson, Ref Sanchez

Links: IMDb, Movie posters, Movie stills