The Dragon's Eye — Dugald A. Steer

The precious Dragon's Eye jewel has the power to reflect the true Dragon Master, the keeper of the fates of all dragons. When evil dragonologist Ignatius Crook sets his sights on the jewel, Dr. Ernest Drake must put a stop to his criminal plans. Luckily Dr. Drake has help -- his two newest students, twelve-year-old Daniel and his sister, Beatrice, have carefully studied dragonology and are ready to use their knowledge to find the jewel. But only true dragonologists will be able to win this race against time.