Unicorn Island: Beyond the Portal - Donna Galanti - Bog

"Just as Sam resigns herself to never knowing the truth about her mother's disappearance, she and Tuck stumble upon a coded verse in The Unicorn Protector Creed. Could using it to travel to the unicorns' ancestral home help her find the answers she's been searching for? When the land beyond the portal reveals itself to be one plagued with ancient and dangerous problems, Sam and Tuck find themselves in a race against time to protect the creatures they love and save this world from a terrible fate of its own making"--