Richard and Alexis Castle are on a transatlantic flight towards London. Richard is scheduled to give a speech for a Sherlockian society, while Alexis plans to meet old friends who live in London. During the flight, Air Marshal Kyle Ford is murdered. The Castle duo are asked by the airplane's crew to investigate the murder. They maintain contact with their police associates in New York City, but can not request reinforcements until the airplane lands. They soon find out that a male passenger is traveling with a stolen passport, and that a female passenger is traveling in disguise. But back in New York, the police discover that Kyle was not supposed to take part in this flight. Kyle's financial records reveal that he had received a large payment from a German businessman, for unknown reasons. The Castles have to find out what was Kyle's agenda, and whether the murder was only part of a wider criminal scheme.
—Dimos I