S04E02 - Death in the Clouds

Frustrated with the evident artificiality of the blowpipe: an item that could hardly have been used without being seen by another passenger, Poirot suggests that the means of delivering the dart may have been something else. Is it the flute of one passenger, or perhaps one of the ancient tubes carried by one of the two French archaeologists on board? Or maybe Lady Horbury's long cigarette holder?

Poirot's focus is upon a wasp that has been seen in the compartment and which provided evidence for the original theory of the cause of death. Without explaining himself, he asks for a detailed list of the items in the possession of the passengers, and finds an incriminating clue: Norman Gale, a dentist who has seemingly never been in the area of the plane where the victim was killed, and has no apparent motive for committing the murder, had an empty matchbox and a lighter. He appears to be the killer, but how can he have committed the murder, when he was apparently in conversation with Jane Grey (the novel's effective heroine) throughout the flight? And why would he have committed the crime? And why were there two coffee-spoons in the victim's saucer?