A Present for Aunt Addie

Harry is confused when his Dad tells him that his Aunt Addie needs something. He is not even aware that he has an Aunt Addie, and more confusing, his dad tells him she is his great-great-great aunt making her far too old to still be alive. But, obedient to his dad, Harry follows the indicated path and after a number of confusing twists and turns, finds and old but youthful woman and a unicorn living in a bucolic setting. Could she really be the little girl who wondered away from the family homestead over 150 years ago? And what could she possibly need from Harry?