Amy, Dan and Nellie arrive in England and find out their lead is William Shakespeare. The team goes to a play of his, his birthplace, and finally, his grave. Dan finds a hidden message in the statue and the siblings decide to return that night. They return that night and dig up his grave in which they find a strange shaped metal pole with the repeating lines "Madrigal Stronghold • Cahill Ancestral Home• Madrigal Stronghold..." and also a long ribbon. Dan memorizes the letters on the ribbon and the other Cahills arrive asking for the lead. Amy destroys the ribbon and they run away with the metal pole. Nellie meets them outside in her car in an alley and they jump in. Nellie prepared to leave with everything early, so Saladin and their bags are already there. They recreate the ribbon and wind it around the pole which gives the coordinates "Fifty Three degrees N Six degrees W. They enter it in the GPS which shows just water. Dan convinces the pilot to bring them there where there is an island. Because the pilot is paranoid about safety he lands them on the beach instead of the cliff where they see a door with a panel next to it. The Holts show up on a boat explaining that they placed a tracking device on Nellie's car and followed them across the ocean. While they climb, Hamilton tells Eisenhower how he thinks they should share the prize with Amy and Dan because of all the help they gave him. Throughout the book he'd been protecting Amy and Dan from any danger that came across them. They come down and take Dan up with them to help open the door. He finds out he didn't even need to do anything and it opened anyway. Scared that Eisenhower would now want to kill him, Dan accidentally knocks himself and Hamilton off the cliff, but since they were attached to ropes Eisenhower was able to pull them up. He punches Dan because he almost made him lose Hamilton, who knocks his father aside in Dan's defense. Dan tells Eisenhower that it was like when he was there the night Hope and Arthur were killed. They all go through the door which is an elevator and takes them down again. Madison, Reagan and Amy get into the elevator with Jonah, the Kabras, and Alistair. The elevator says in a mechanical voice that it won't go up until it gets a retinal scan from a representative of each branch. Last when it comes to Madrigal, the non-Madrigals start arguing that they aren't a branch. Jonah explains how Dan had called himself a Madrigal and could fool the elevator. Dan tells the truth of his branch and Eisenhower is about to throw him out of the elevator, but accidentally lifts him past the retinal scan. In the confusion, only Hamilton, Alistair, Jonah, Ian, Natalie, Dan and Amy get in. They go back to the top, and Hamilton insists for them to wait for the rest of the Holts to climb up, but they still go back to the panel next to the door and each branch representative touches it when they get back in. The back wall opens and they go to a spiral staircase. Hamilton wants to wait for the rest of the Holts, but instead Sinead Starling comes in. She sees a plaque saying "ON THIS ISLAND A FAMILY SPLIT APART. ON THIS ISLAND A FAMILY CAN REUNITE" and thinks it's an anagram. Amy opens the door explaining the Madrigals' true purpose. The group goes into the gauntlet that is a test to see if they are capable of getting the prize: the master serum. While in the gauntlet, there is a small explosion and rocks begin to fall from the ceiling. Jonah gets hit by a few of the rocks and gets knocked out. On the way, Natalie and Ian explain that they fooled Isabel into thinking the clue was in Washington, and they didn't have much time before she caught up. Strangely, the doors in the gauntlet with the questions on them are all hanging open on their hinges. When they reach the remains of Gideons lab, they rush through room after room. When Dan and Amy reach the last room, they are confronted by Isabel who is holding the Cahill serum and a gun. When Hamilton attempts to charge her, she fires a warning shot. She commands Ian to go fetch Jonah, who had broken his legs in a rockfall and been left behind in the rush. When Ian and Natalie refuse to further obey her in realization that she didn't care for their lives as long as she could win the hunt, she disowns them. Isabel threatens Ian by threatening to shoot Natalie. Ian persists, thinking even Isabel wouldn't shoot her own daughter, but she shoots her in the foot. Natalie pretends to be in pain, but Isabel threatens to shoot anyone else in a more serious part. She explains that the serum is fake and that each branch representative, including Madrigal, must touch the vial for the final clue. When they do, a shocking hologram reveals that the final clue is not an ingredient, but the serum formula. Isabel shows in surveillance cameras that she had been watching them the entire time and that she tied Nellie, the helicopter pilot, the Holts, Broderick Wizard, and Ted Starling to the tombstones outside on the beach with remote control explosives to "persuade" the others to reveal their clues to her silently. During this time, it is revealed that Ted Starling was blinded and Ned Starling has extremely bad headaches. When they have all given her their clues, she follows the instructions on the vial and finds the ingredients in the rooms. She finishes the serum and is seconds from drinking it, when Ned Starling runs in, holding his head in pain. Isabel sets down the serum and aims her gun at Ned. Amy, Dan, and everyone else including Jonah and Natalie tackle her. Ian is about to destroy the serum but Sinead argues that she needs it to cure her brothers and some of them begin to fight over it. Finally Amy gets the vial with the Cahill serum and smashes it against Isabel. Isabel faints and the serum is completely obliterated. Alistair feeds Isabel a pill that Irina Spasky invented which would ensure Isabel would forget the past few hours. The Cahills finally forgive each other for past wrongs and reunite, fulfilling Olivia Cahill's final wishes, despite the fact that not all the members are together. The clue hunters write down and give their clues to Amy and Dan, since they earned it, and they win. Alistair finally makes amends for not taking action when Hope and Arthur died. He decides to turn Isabel over to the police for murder, so Isabel Kabra will be in prison for the rest of her life. Outside they free everyone and William McIntyre tells that whoever survived the gauntlet got double the amount of money that they lost when they had joined the hunt and refused the million dollars. Everyone leaves in high spirits until there are only Madrigals on the island. William gives them a note from Grace that gives her pride and gratitude to them for succeeding. Fiske and William, on Dan, Amy, and Nellie's persistence, reveal that one of the most important reasons that the branches have to reunite is that there is a rival family of the Cahills, the Vespers, that is so shadowy and secret that they make Isabel Kabra seem like Mother Teresa. They have long since wanted to gain Cahill powers. Amy and Dan decide to go back to their simple apartment in Boston, Massachusetts even though they and Nellie are now rich, and will return after recovering to face this rival family, but for now they will just go home.
- Ted Starling
The Clue is the Serum Formula.
Secret MessageEditVespers Are Coming
This letter is from Grace for William. She writes that the news from her doctor isn't good and she will die soon. News on the front are worst: The Vespers are drawing near. She hopes that the hunt will help Amy and Dan bring this family together. The devil is at the door, this family must fight the real enemy.
Unlike most books this includes one card from each branch, all of them are needed for a puzzle, and they're all agent cards.
It's showing the characters that participated in the gauntlet while also giving a short description of them for the card name. Names from top to bottom are Amy, Dan, Jonah, Hamilton, Alistair, and Natalie.
When you put these cards next to each other, they show a scene from the gauntlet.
These cards together form the message ONLY TOGETHER CAN WE FIGHT THE TRUE ENEMY in the order of cards 220,225,224,223,222,221,223,224 and 225.
Card 220: The Last Chance has a image on the back that can be arranged with 9 cards from the other books to make the scene of Gideon Cahill's lab fire.
This is only able by listening to the bonus track on the audio book. In it, Grace leaves a final message to Amy and Dan. She says that by now, the two has learned the entire truth and that they had inherit a few more things. She leaves her bungalow from the Madrigal Gauntlet, her headquarters in Madagascar, and the Flying Lemur. She also says in her Swiss Bank Account are a couple of her personal belongings she didn't want to keep in the mansion from Hope and Arthur. Amy receives a necklace Hope got on her eleventh birthday right before her father died. Dan gets a watch Arthur had that is damaged from many attacks. And from Grace, a ring. She ends the recording saying goodbye and that she loves both of them.
- The book gives everyone in the clue hunt's point of view.
- On the front cover, the key in the logo is usually behind the U in Clues. But on the cover of this book, the key is seen flying out of the U. A guess might be that the U is made of an elastic material that, if something hits it, will pass through it. This is again seen is in the promotional videos for Vespers Rising.
- Also, the other four keys are flying outwards from the logo. This probably means that those keys are also in the logo, but hidden from view.
- On the spine of each book, the title of the book has a bright glow around it. But on the spine for this book, there is no glow.
- It is the longest book in series 1.