Poirot, who was present at the restaurant, intervenes. He reveals that Pauline is not dead; he had anticipated the killer's move and switched the poisoned glass. Poirot then exposes as the murderer.
In , Season 5, Episode 3, titled " The Yellow Iris ," Hercule Poirot is drawn into a cold case that began two years earlier in Buenos Aires. The Backstory: Buenos Aires Poirot subtitles English S05E03
Two years ago, Poirot was in Argentina when he was invited to a dinner party hosted by . During the meal, Russell's wife, Iris , died suddenly after drinking champagne poisoned with cyanide. At the time, the death was ruled a suicide, but Poirot remained unconvinced. However, local political unrest forced him to leave the country before he could complete a proper investigation. The Present: A Second Chance Poirot, who was present at the restaurant, intervenes