Poirot has to execute the final wishes of an old friend who has been killed.

Poirot returns to Belgium for the first time since the Great War. There he revisits a twenty-year-old murder mystery that was never officially solved.

Poirot and Hastings are at Lake Windermere for an attempt on the world speed-boat record. An elderly widow is hurt by falling down stairs, then later killed by poisoning with phosphorus.