With their parents off to London on a special trip, Hannah, Zachary, and Sarah Emily are thrilled to be going back to Aunt Mehitabel's house on Lonely Island. Though their favorite aunt can't join them, they know their tummies will soon be filled with Mrs. Jones's mouthwatering cookies and their minds full of Fafnyr, the fabulous creature they befriended last summer. The glittering three-headed dragon remains safely hidden in a cave high above the ocean, waiting for the children's return. But is Fafnyr's hiding place safe? As the children nervously discover, a white yacht is now anchored off the private island, and a crew led by billionaire J. P. King has been scouring onshore, supposedly watching birds. The children have promised to keep Fafnyr's existence a secret, but it's hard to know if the smooth-talking Mr. King is friend or foe. Only Fafnyr's own stories can lead the Dragon Friends to the heart of the mystery, as they teach the children to think more clearly, to make the right decisions - and to discover what's worth fighting for.