David Suchet (Henry VIII, The Way We Live Now) stars as suave Belgian super sleuth Hercule Poirot in these new mysteries based on the novels by Agatha Christie. Whether he's on holiday abroad, taking a countryside break or simply going about his business near his central London home, Poirot finds himself exercising his "little grey cells" by helping police investigate crimes and murders, whether they ask for his help or not. "Third Girl" - Poirot finds he cannot ignore the pleas of a young heiress when she approaches him with the bizarre claim that she may be a murderer. Soon the heiress' childhood nanny is found dead, leading Poirot to team up with crime novelist Ariadne Oliver in order to solve one of the most baffling cases of his career. Zoë Wanamaker (Harry Potter) guest stars.