Set sail to Atlantis with Tim and his friends in the laugh-out-loud funny, highly illustrated fourth book of the New York Times bestselling Once Upon a Tim series from Spy School author Stuart Gibbs. Tim and his ragtag crew have been rescued from certain doom by a mermaid princess--but now, she wants something in return for saving their lives: her father King Neptuna's stolen trident. To pay their debt, Tim, Belinda, Ferkle,...