This modern fantasy novel set in London -- for children ages 8 to 12 -- tells the story of Elizabeth, a twelve-year-old Canadian girl who feels homesick and lonely after her mother's death when her father moves them to London. Soon, however, she meets an assortment of unusual characters and a strange adventure unfolds. Among her new friends is Maud, the homeless woman in the park, who befriends her and teaches her the magic of the great chestnut trees. But friendship works two ways and soon Elizabeth must shoulder Maud's job as "Keeper of the Trees", protecting the tiny horses which run from the Otherworld to support life on Earth. Evil forces appear in the shape of the Hunter whom Elizabeth must face as she battles to keep alive the trees on whose survival hang the lives of many people, including Elizabeth's young friend Thomas. The high seriousness of her role hits home when Maud explains, "Each species lost takes a thread from the fabric of life." Lines of classical poetry strengthen mood and theme in a tale which links past to present, country to country in a celebration of the natural world. Readers walk the wire between the real and the unreal, carefully lured into the fantastic by Brenna's skillful depiction of the everyday, then whoosh -- the reader balances on something hardly to be believed . . . but maybe. . .