Dumb Witness (S06E04)

Poirot and Hastings travel to Lake Windermere to witness a bid for the world speed-boat record. Their visit takes a dark turn when an elderly widow suffers an accident, tumbling down the stairs. Tragically, her situation worsens as she is later discovered to have been poisoned with phosphorus. As Poirot investigates the mysterious circumstances surrounding her death, he uncovers a web of intrigue that complicates their idyllic getaway.