Sunbeam, a young teen, is a spunky, impulsive outcast whose fierce devotion to find her missing twin sister is threatened by a chilling, dark presence. Sunbeam's twin, Gilda, diappeared five years ago. Worse, Sunbeam never knew her father; he mysteriously left the family. So she lives with her mother, who always references a nameless threat but never answers her questions. When Sunbeam finds a mysterious Golden Key, she and her loyal horse, Whitewing, are catapulted into the Depths of Cypress: a shadowy forest where she discovers traces that propel her forward. Along the journey, she realizes she is only a step from death after she finds clues about the island's hidden secrets. Whitewing sticks close by her side as they try to escape the cryptic Depths alive--and most of all--uncover the truth about Gilda.