The Willow Maiden by Meghan Collin’s

Enter a realm of mystery and magic, where an ordinary man falls in love with a maiden of extraordinary origins; where a perilous underwater battle is fought before he can wed her and a great sacrifice must be made to keep her.One Midsummer's Eve, when the Willow People emerge from their trees to celebrate, Denis is captivated by Lisane. With her help he competes in a deadly game imposed upon all mortals and waits patiently for autumn to marry her. Yet, after a blissful winter together, spring comes and Lisane must return to her tree.Now how can Denis bear to let her go?