The Sword Thief
Peter Lerangis
 The book starts with Dan and Amy in a Venice airport. There, Ian and Natalie Kabra steal their plane tickets and board a plane with their au pair, Nellie Gomez, who is already on the plane. Amy and Dan are then forced to team up with Alistair Oh, their uncle, and fly with him on his private plane to Tokyo, Japan. Together they learn about Toyotomi Hideyoshi, the greatest warrior in the history of Japan, and the son of the first Tomas. The Holts kidnap Amy, Dan, and Alistair and threatened them into helping them find the next clue. They are pulled into a room by Alistair after nearly being killed by the train. In this room, they find a haiku, which tells them to use geometry to find Hideyoshi's treasure. Later, they find some geometric shapes, but are chased by the Yakuza and are once again nearly killed. They are rescued by Nellie, who has struck a deal, and is accompanied by, the Kabras. When the Kabras give Amy and Dan a small coin of importance to the search, the two Cahills agree to join forces with the Kabras. They decode another message in the shapes. The message tells them to go to Korea. In other parts of the story after they meet the Kabras once again, Amy falling for Ian is introduced in this book. The author's writing also gives a little hint away: Ian may admire Amy, and Dan suspects it as well. In Korea, everyone goes to Alistair's house. There, they look at old books about the Cahill family in Alistair's secret library. By reading one of them, Amy and Dan figure out that the secret of the 39 Clues is the ability to make gold out of lead. They also figure out that they should go to a mountain called Pukhansan. On the mountain, they find an entrance, and open it with the coin they have. Inside, they find all of Hideyoshi's treasure, and the third clue, gold. The Kabras have a plan, but little do they know that Dan also has a plan. He discovers an anagram and says the next location is Lake Tash, Kyrgyzstan. The Kabras then betray them and block them inside the cave. Dan then tells Amy that he tricked the Kabras into thinking that Lake Tash was the next location, and the two figure out that it's actually an anagram for the words, Al Sakhet and Alkahest, the alchemical word for the philosopher's stone. Dan and Amy make it out but Alistair appears to be crushed under falling rocks. They also see Bae Oh talking about this with The Man in Black. Upon returning to Alistair's estate, Dan sees Alistair's gloves (which he was wearing before the cave in), and realizes that he isn't dead. They also figure out that the next clue is in Egypt. The adventure continues in Beyond the Grave. This is where they will find the fourth clue. The book ends with Bae Oh, sitting his office. He pages his secretary but Alistair answers instead. Alistair threatens his uncle, and when Bae looks in his receiving room, no one is there.