Agatha Christie's Poirot (1989)

S2E9 The Adventure of the Western Star

Belgian actress Marie Marvelle is alarmed when she starts receiving ominous letters from a mysterious man, demanding her prized possession, the Western Star diamond. Concerned for her safety, she turns to her old friend, detective Hercule Poirot, in London for assistance. Poirot eagerly takes on the challenge, determined to protect Marie and uncover the truth behind the threats.