Summer 1904. Katharine and her best friend, Margaret Goodwin Meacham, are thrilled to attend the St. Louis Exposition for the centennial celebration of the Louisiana Purchase. Not only is it a grand event, it's also the first time the young women have traveled together alone, and they are giddy with excitement—despite warnings from Katharine's family friend, poet Paul Laurence Dunbar, to be careful.

Undaunted, the girls have a lovely time—until the exposition turns from a girls' trip to a misadventure when they stumble upon a woman in distress. It's obvious that she has been attacked. Katharine and Margaret do their best to save her, but the woman dies. Yet just before her last breath, she utters the words Aeronautics Competition. Katharine's brothers, Wilbur and Orville, were asked to enter the competition with their successful 1903 flyer but declined. Katharine, of course, knows they would have won and has confidently said so to anyone who will listen.

Now, unable to get the woman's face out of her mind, Katharine can't help wondering whether her death could somehow be connected to her brothers' flying machine. Katharine convinces Margaret to join her investigation—and it's soon clear that someone will stop at nothing to get the Wrights' invention to the masses. But with Katherine on the case, they may be in for a hard fall.