The Wings of Poppy Pendleton by Melanie Dobson

In this compelling new time-slip mystery, a little girl goes missing from her family's castle in the Thousand Islands of New York. Eighty-five years later, a journalist teams up with a woman living on Koster Isle to find out what happened to Poppy, once and for all.

1907. On the eve of her fifth birthday, Poppy Pendleton is tucked safely in her bed, listening to her parents entertain New York's gilded society in their Thousand Islands castle; the next morning, she is gone, and her father is found dead in his smoking room.