Into The Gauntlet by Margaret Peterson Haddix

In the thrilling conclusion to the 39 Clues series, the Cahill siblings, Amy and Dan, find themselves in a high-stakes race against time as they navigate a web of deceit and danger to uncover the final clue. With the fate of their family and the world hanging in the balance, they must confront their deepest fears and make impossible choices. As alliances shift and secrets unravel, Amy and Dan must rely on their wits, courage, and each other to outsmart their rivals and solve the ultimate puzzle that could change everything.

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