In mentioning a new restaurant in London, Hastings reminds Poirot of his only unsolved case. Two years ago he was in Buenos Aires, Argentina, at a restaurant of the same name, when a woman at a nearby table, Iris Russell, died of cyanide poisoning. It looked like suicide, but Poirot believed it was murder. However, before he able to investigate her death he was deported from the country - Argentina was in the middle of a coup and Poirot was persona non grata. The London restaurant's name is not a coincidence and Poirot now has a chance to reopen his investigation.
—grantss