The author has flown gliders and even built one herself. And her story about the Elizabethan man and his two young assistants who constructed a flying machine from Leonardo de Vinci's plans, is, as might be expected, strongest on mechanical details and on information about the assumptions and knowledge of flight that existed at the time. Adam de Mountforde is the wealthy experimenter; Roger and Margaret are the village children who come to help him. As others begin to spy on them, the secret is nosed out and the three are suspected of witchcraft. After a couple of trial runs, they just barely manage to save themselves from immolation by effecting an escape on the mechanical bird. The characters and the historical detail outside the laboratory are superficially covered, but the sense of adventure, the intriguing concept, and the hint of a romance between Margaret and Adam make this a pleasant book.