Nancy goes to the ExcelloFlying School in the Midwest to take lessons while her friends Bess and George perfect their horse riding. At once, the young sleuth is confronted with the mystery of a hijackedplane and a missing pilot. Then the rancher's prize pony, Major is stolen. Nancy becomes a detective in a plane and on horseback to track down the elusive sky phantom and the horse thief. A lucky find – a medal with a message to be deciphered on it – furnishes a worthwhile clue. Romance is added when Bess becomes interested in a handsomecowboy. Readers will spur Nancy on as she investigates a strangemagnetic cloud, hunts for the horse thief, and finally arrives at a surprising solution.