Into the Gauntlet is the tenth book in The 39 Clues novel series. It was written by Margaret Peterson Haddix and released on August 31, 2010. In the beginning of the book, Amy and Dan are now at the end of their clue hunt, and every misfortune they've had. Their lead is a poem found in their hotel room. However, it is then stolen by Isabel Kabra. It is revealed that William Shakespeare was a powerful Madrigal and the most important clue is on the line against their competitors. Dan and Amy are supposed to go to the Globe theater to watch a Shakespeare play, Romeo and Julliet. While watching the show they see what looks to be ninjas. The ninjas find a clue at the top of the theater but drop it into the hands of Dan and Amy. As it turns out the whole Cahill family is at the play looking for the clue. Backstage of the play the fight over the paper found at the theater. Mr. McIntyre and Fiske Cahill reveal there is another family out there that makes Isabel Kabra look like Mother Teresa. The globe on the 39 Clues symbol is, unlike in the first nine books, shattered into pieces. The message on the cards is, "Only together can we fight the true enemy." The secret message in the book is "The Cahills aren't the only ones looking for the Clues. The Vespers are coming."
Plot
Into the Gauntlet begins as Amy and Dan Cahill enter a London hotel tired and with no lead whatsoever. They receive another lead, but this is stolen by Isabel Kabra via a pet monkey, who leaves them a coin with a fancy script K on it. However, Dan, who has already memorized it, rewrites it. Amy looks all over the Internet to find out what it means, and she is about to shout out when Nellie realizes that the Kabra coin is a bug. She destroys it, along with three other bugs from each of the other three branches. Amy then tells them that the clue leads to William Shakespeare, so they go to a performance of Romeo and Juliet in The Globe Theatre. Once there, they confront the Starlings, who are back in the clue hunt after being sent to the hospital in an explosion back in The Maze of Bones, and steal their lead, but they are trapped by Jonah Wizard, who was forced back into the clue hunt by Cora Wizard, the Holts, Alistair Oh, and the Kabras. Hamilton Holt steals the piece of paper with the lead, but Dan rips off the top and bottom, and he and Amy run away while everyone else is fighting over the rest of the lead. Their section of the lead says: "For this great man we sing was b here". The rest of the word that goes with the letter "b" was torn off, so they assume that it was supposed to be "born". At Shakespeare's birthplace, Amy and Dan realize that the word was supposed to be "buried" and are the last to arrive at Shakespeare's grave site besides Isabel Kabra, Eisenhower Holt, and Cora Wizard. However, they are surprised to find that no one is fighting with each other and are instead making unsuccessful exchanges of clues and information. The teams eventually leave the Cahills in the grave site with video cameras, but they are aware of this and communicate by writing on a sheet of paper while pretending to draw a picture of Shakespeare. They then go outside to Shakespeare's grave, and Dan does a rubbing of it. However, just as Dan finds a secret line that does not show on the tombstone, the other teams arrive. Dan pretends to mess up and tears the paper apart, careful to rub just the first four lines when someone from each team asks for a rubbing. Once everyone leaves, he makes a rubbing for them but includes the last four lines, in which Shakespeare asks them to dig up his grave. Inside Shakespeare's grave, Amy and Dan find a metal pole with the words, "Madrigal Stronghold * Cahill Ancestral Home" encircling it. They also find a ribbon with seemingly random letters on it but are forced to unravel it as the other teams appear and chase them. Meanwhile, Sinead Starling steals a digitized version of the ribbon from the grave's guardian while everyone else plants a homing device on Amy and Dan, who have recreated the ribbon out of the bottom of Nellie's's old t-shirt and wrapped it around the metal pole to find the coordinates to the house of the original Cahills- a house on an island off the coast of Ireland. The other teams follow them there, but they are forced to work together as they make their way through the gauntlet, a series of doors with questions about the clue hunt. However, every door except the last is opened, and when they reach the vial that supposedly has the master serum, they find that Isabel Kabra beat them to it. She reveals that the serum is fake and forces them to give her all their clues to save the people they love. However, when Isabel is about to drink it, Ned Starling bursts into the room, and she turns towards him, about to shoot him with her gun. Everyone unites and charges her, knocking the gun and the serum out of her hands. But then only Amy and Dan are holding her down while everyone else chases after the serum, and she reaches the gun, knocking Dan in the stomach with it. She is about to shoot him when Amy, out of options, grabs the vial with the serum and slams it down on Isabel's head. It shatters, destroying the serum, but everyone gives Amy and Dan their clues because they were the only ones that held down Isabel while they all chased after the serum. After finding their way out of the gauntlet, the teams separate on amiable terms, and Amy and Dan stay behind with Fiske Cahill and Mr. McIntyre, who give them a letter from Grace. They then reveal that the entire Clue Hunt was just a preparation for the battle with another family. Amy and Dan are left in the legal custody of both their Great-Uncle Fiske and Nellie, but the letter makes it clear that their adventures aren't over yet.
