Myrtle Hardcastle has no desire to go on a relaxing holiday excursion with her aunt Helena when there are More Important things to be done at home, like keeping close tabs on criminals and murder trials. Unfortunately, the twelve-year-old aspiring detective has no say in the matter. So off Myrtle goes—with her governess, Miss Judson, and cat, Peony, in tow—on a fabulous private railway coach headed for the English seaside. But before the train reaches its destination, Myrtle and Peony discover a dead body in the baggage car. Someone has been murdered—with Aunt Helena’s sewing shears. The train trip is derailed, the local police are inept, and Scotland Yard is in no rush to arrive. What’s a smart, bored Young Lady of Quality stranded in a washed-up carnival town to do but follow the evidence to find out which of her fellow travelers is a thief and a murderer?