Napoleon's invasion of England is hidden in the clouds... It is 1819, and Cornwall is agog at the daring of the two young lady aeronauts who, earlier in the summer, flew nearly to France and back in their homemade air ship. Much more is riding on Loveday Penhale and Celeste Blanchard's new and improved vessel-they plan to win the Tinkering Prince's prize, offered to anyone who can help England win the war against Napoleon. To their dismay, they must take two local gentlemen aloft to report on the ship's capabilities. While Captain Trevelyan and Emory Thorndyke are welcome in drawing room and ballroom, their presence on the air ship proves disastrous. Wildly off course, Loveday barely manages to bring the vessel down safely-in France! Now it is up to the gentlemen to keep the newly designed ship hidden while Loveday and Celeste secure supplies for its repair from Celeste's former home, l'Ecole des Aéronautes in far-off Paris. But much has changed since Celeste left the capital, and enemies lurk in its very walls. With her famous aeronaut mother dead in suspicious circumstances, and the flight school closed, there is only one thing to do-make up a story about her absence and approach Napoleon himself. He promptly makes Celeste his Chief Air Minister, and commands her to plan the invasion of England by air. Can she and Loveday stay alive in this nest of vipers long enough to help their stranded friends? Before they are unmasked as spies-and before their beautiful air ship is captured and used to attack England?