Murder at the Gallop (1963)

Murder at the Gallop (1963) The old and wealthy Mr. Enderby dies of a heart attack but the ever suspicious Miss Marple has her doubts. Who or what gave him a heart attack? Enderby's poor relatives gather at the The Gallop, a combined boarding-house and riding school. Miss Marple also gets there to find out if any of them had any particular reasons to see him dead.