Isle of the Piper. Tanqueray, #3

Horry is still coming to terms with the knowledge that his small, beautiful, and very greedy pony, Fleur-de-Lis, is really a long-lived kelpie, and that he won't see his best friend Vigdis for a long while. His sister Ancella, newly married and expecting a baby, is determined to visit a mysterious island and track down the piper who gave her an enigmatic hint back at the New Year's ball. With spring almost ended, Ancella sets out on an adventure, taking Horry as her companion.
The eldest and the youngest of the Tanqueray siblings have a special bond, but there are challenges to overcome before they find the answers to their questions.