In the thrilling sequel to Guardians of the Gryphon's Claw, an epic adventure novel that "is sure to keep lovers of Rick Riordan running to the shelves," Sam London dives headlong into his second case involving a selkie, a mysterious girl, and an ominous new threat to the mythical and human worlds ( School Library Journal )! Sam London didn't mean to uncover an ancient secret, but when he found out that mythical creatures are real and living in our national parks, he became the newest recruit to the Department of Mythical Wildlife. Ever since, the middle schooler has been anxiously awaiting the call for his next case . . . and it finally arrives with the brazen appearance of a selkie in San Francisco Bay. Along with Dr. Vance Vantana and the guardian Tashi, Sam pursues the selkie, who has taken a peculiar interest in fashion's newest "it" girl and social media star, Pearl Eklund. But the closer he gets, the more questions emerge about Pearl's mysterious connection to the mythical world. Is she the long-lost hope for an entire civilization or the harbinger of its doom? It's up to Sam to find out the truth, and fast. . . . The fate of humanity hangs in the balance. Praise for Guardians of the Gryphon's Claw, Book One: " A death-defying, globe-spanning adventure , packed with creatures out of folklore and myth." --Publishers Weekly " So original and exciting. This is the best fantasy-adventure novel I have read in some time." --Martin Olson, New York Times bestselling author of The Adventure Time Encyclopaedia