Twenty-one people have boarded the "Prometheus" at France"s Le Bourget airport for a routine, one-day flight to London. But what begins as an ordinary excursion over the English Channel turns into a most extraordinary case of murder when a female passenger is shot with the venom-tipped dart of a South African blowpipe. Even more bizarre is that the killing could go completely unnoticed by any other passengers-including Hercule Poirot, the brilliant Belgian detective, sitting not fifteen feet from the victim.