|Cave of Wonders|
|Publication date||August 27, 2013|
| Preceded by|
Curse of the Ancients
| Followed by|
Behind Enemy Lines
Europe is in the grip of the Dark Ages, but there is a light in the dark: Baghdad. The great city has become a center of learning, populated by scholars, merchants, and explorers from all across the known world. But danger lurks in the desert ... and Dak, Sera, and Riq must act fast to save the world's greatest library from utter destruction.
The book comes packaged with a full-color, two-sided, collectible Hystorian's Guide, a player's strategy guide to the online adventure.
Follow the map, study the Guide, and save history!
The book starts with the trio warping to the desert near Baghdad. They ‘join’ a caravan that is going into the city and once they’re safe, they activate the SQuare.
The Hystorians say that it’s the year 1258 in Baghdad, and that the trio’s task is to save the library at the House of Wisdom or, more specifically, the writings of Aristole that are in there. The Hystorians also say that, because of the Break, the SQuare has no info on the Prime Break, so the trio will have to pick up a new SQuare along the way. Finally, Arin says that they have no idea who the local Hystorian in Baghdad is, or where to find him/her.
Dak figures that the Hystorian would probably be in the House of Wisdom, with Aristole’s works. Along the way, in order to earn money for clothes, Dak tells a story very similar to the Great Break in the book and is subsequently caught by the Market Inspector. They aren’t caught, thanks to a rug seller named Farid, and go on their way. At the House of Wisdom, they meet Abi, a man who reveals that he is the local Hystorian.
The trio explain to Abi what the Break is and he says that there will be no way to stop the Mongols. Instead he suggests asking Tusi, the Mongol leader’s advisor and a scholar whom Sera admires, to spare the libraryThe next day, they meet with the caliph, the ruler of Baghdad, and request an audience with Tusi. The caliph allows them to see Tusi, but he refuses to ask Hulagu Khan, the leader of the Mongols, to save the House of Wisdom, saying that doing so would lead to death. His adamant refusal leads Dak, Riq, and Abi to believe that Tusi is SQ, although Sera still has faith in him.</p>
The group decides that the only way to fix the Break now is to speak with Hulagu themselves, and Abi sneaks them into the Mongol war camp, though he himself doesn’t come. At the camp, Dak pretends to be a spy in an attempt to speak with Hulagu, but he and Riq are captured instead and do not get to see him. Sera decides that fixing the Break is more important than rescuing her friends and attempts to convince Tusi one more time. Although she finds out he is not SQ, he still doesn’t agree to speak for the House of wisdom, and loses some of Sera’s respect for him.
Meanwhile, Dak and Riq are brought to the ‘Divine Man’, a general named Guo Kan who had yet to lose a battle. The general reveals that he, along with the Market Inspector and the vizier of Baghdad, are SQ. The two are imprisoned in his tent but manage to escape with Sera. The trio leave the camp and sneak into Baghdad that night. Upon their arrival, however, they’re captured and imprisoned once they say they’re friends with Abi, who was declared a traitor. After a failed attempt to pick the cells’ locks with parts from the SQuare, leaving it in a fragile condition, they escape by placing silk in the locks, allowing the doors to unlock for the guards to bring them food, but preventing the cell doors from locking again
The four split up-Dak and Sera go try to fix the Break, while Abi and Riq go and retrieve the Infinity Ring, which the vizier took. After having a run-in with a bear, the pair face the vizier and his guards. The vizier is left hanging off the balcony, with a tiger below, and gives Riq the Infinity Ring in exchange for help up. Once the vizier is on the balcony, however, he attempts to retrieve the Infinity Ring but stumbles off the balcony instead. It is not revealed what happens to him.</p>
Meanwhile, while Dak and Sera are walking, Sera tells Dak about her seeing the Cataclysm. Dak assures her that she will see her parents alive one day and save them, along with the whole world. Shortly afterword, they see Farid, the rug merchant from earlier, who explains that a man and a woman-Dak’s parents-told him to wait for Dak and Sera. They stay at his house a few days, as there’s nothing they can do before the Mongols entered the city
The day before they did, however, Farid was visited by the Market Inspector, who is going to confiscate his rugs. Dak and Sera hide in the rugs and are brought to the palace Hulagu Khan is living in. Once there, they hide in a cabinet in the reception hall while waiting for Hulagu to come. Once Hulagu comes, Dak and Sera exit the cabinet and are soon caught by General Guo Kan, who tells Hulagu that the kids are assassins.
At this point, Tusi steps forward and, supporting Dak and Sera, tells Hulagu that how he deals with the children will be very important, and takes Dak and Sera to ‘interview’ them in private. The three come up with and execute an idea-they tell Hulagu that he needs to build an observatory to study the stars-complete with books from the library. Despite Guo Kan’s objections, Hulagu agrees, and gives them a week to remove whatever books they want from the library before it’s destroyed.
Dak, Sera, and Tusi meet up with Riq and Abi, but before they can take Aristole’s works, the Market Inspector starts burning the library. Thankfully, they manage to save Aristole’s works and flee the library. Once Abi and Tusi are out of sight, the trio warp to their next location.
In the epilogue, the kids warp to the Mississippi in 1804, the starting location for The Lost Expedition. Dak explains what happened that year-the Louisiana Expedition-and the trio walk to St. Louis, only to find out the city has been taken over by the SQ.