Agatha Christie's Partners in Crime

Season 1, Episode 3: The House of Lurking Death

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After residents of Thurley Grange are poisoned by arsenic in a box of chocolates, owner Lois Hargreaves hires Tommy and Tuppence to investigate the incident. Before they can arrive on the scene another poisoning occurs with deadly results leaving Tommy and Tuppence the task of discovering the murderer among the remaining suspects.