The Sword Thief is the third book in the series. It was written by Peter Lerangis (who will also write book #7) and was released on March 3, 2009. In the book, Amy and Dan track the life of one of the world's most fearsome warriors in Tokyo, Japan, Toyotomi Hideyoshi, in a bid to uncover whether he is a Cahill, and if he possessed a Clue. Alistair Oh, on some unknown promise that he kept to Amy and Dan's parents, helps them. They also make an alliance with Ian and Natalie Kabra. Later, they go to Korea where they find the third Clue, gold. The Kabras try to kill Amy, Dan, and Alistair by trapping them inside a mountain. Amy and Dan escape, thinking that Alistair had died, but he somehow escapes. Amy and Dan then figure out that the next clue is in Egypt. In this book, Amy and Dan also discover what the main Cahill secret is: the philosopher's stone.