The Mysterious Affair at Styles (S03E01)

After enduring the traumas of World War I, British Army officer Arthur Hastings seeks solace at a tranquil country manor in rural England. However, his respite is shattered when the estate's matriarch succumbs to strychnine poisoning overnight. Determined to uncover the truth behind the murder, Hastings turns to an old acquaintance, the renowned former Belgian detective Hercule Poirot, who is also staying nearby with fellow war refugees. Together, they delve into the dark mystery surrounding the tragic event.