"The Mysterious Affair at Styles" marks Poirot's first mystery. Interestingly, Poirot's first and last cases take place at Styles.
Here he reconnects with a friend, Captain Hastings, whom he has not seen in some time. Hastings is recovering from an injury he received during World War I. He is staying in a mansion that has been conscripted as a hospital.
In the beginning, we see Hastings and other patients watching the newsreels which shows Belgian refugees arriving in England. This is how Poirot first came to England.
Hastings has an old friend who invites him to his place, Styles Court. He confides in Hastings that his mother has married a younger man, Alfred Inglethorp. The whole family believes that he is a golddigger.
Not long after that, Emily Inglethorp is murdered by strychnine. Hastings appeals to Poirot to investigate. Inglethorp is the obvious suspect, but are things as they seem? This is a beautifully made episode that displays the era with perfection. The story has a couple of holes, but Poirot's deductions are excellent, and even if you know the denouement, you will be intrigued by the way it unfolds.
David Suchet is the best Poirot - fastidious, cheerfully egomaniacal, and eccentric. Delightful episode.