The Hollow

S9 E4: Socialite Lady Lucy Angkatell worries about her family guests arriving for the weekend - they all loathe each other. Inviting Hercule Poirot as a distraction, the weekend is interrupted when philanderer John Christow is found dying by the swimming pool with his wife holding a gun, but who shot him? Poirot soon realises that he is up against one of his trickiest adversaries.