Trust No One

This novel, part of The 39 Clues middle-grade adventure franchise, picks up as Dan Cahill, his older sister Amy, and their friends Jake and Atticus Rosenbloom return to New York City after a mission in Timbuktu. For weeks, the siblings have been forced to steal artifacts at the command of the anonymous Vesper One, leader of the Vespers, a shadowy organization and centuries-old enemy of the Cahill family. The Vespers hold seven hostages, including Amy and Dan's guardians, Nellie Gomez and Fiske Cahill. Dan privately resolves to finish assembling the serum, a formula derived from 39 components that grants superhuman abilities, and take it himself. He is the only person who has memorized the formula.

Upon landing, Amy receives a text from Vesper One directing them to Yale University, referencing the numbers 408 and 74, and imposing a three-day deadline with the threat that "someone pays" if they fail. She forwards the message to her boyfriend, Evan Tolliver, who coordinates operations at Cahill headquarters in Attleboro, Massachusetts. Meanwhile, Evan discovers that Sinead Starling, Amy's best friend and trusted network member, is the mole feeding information to the Vespers. He urgently texts Amy to warn her.

En route to Yale, Jake identifies "408" as the catalog number for the Voynich Manuscript, a fifteenth-century document written in an unknown language that no one has decoded. Jake's late stepmother, Astrid Rosenbloom, studied it for years. On the Whitestone Bridge, a motorcade intercepts the group and Sinead emerges to join them. She steers the conversation toward the serum, arguing the formula should be stored on a device rather than kept only in Dan's memory. Her true aim is to obtain the formula for Vesper One and use the serum to cure her triplet brothers: Ted, who is blind, and Ned, who has incapacitating headaches, both from injuries sustained during the original Clue hunt. She carries a concealed miniature handgun. Amy, trusting her friend, agrees.

At Yale, Amy's phone reconnects and she sees Evan's text: "SINEAD MOLE." Sinead reveals her hatred for the Cahills, blaming the family's competition, organized by their late grandmother Grace Cahill, for her brothers' injuries. She fires the gun; the bullet barely misses Amy's neck. Amy fights back but Sinead escapes. The group discovers a signal-blocking device Sinead planted to delay Evan's warning.

Evan arrives at Yale. Amy calls Ian Kabra, a Cahill operative she had wrongly suspected as the mole, to apologize. Ian shares intelligence: his mother, Isabel Kabra, runs a charity that appears to cover travel to unexplained global locations. Amy sends Evan back to Attleboro to coordinate the hostage search.

The group enters the Beinecke Rare Book and Manuscript Library. When Jake mentions Astrid, the curator brings out the Voynich Manuscript. Dan discovers folio 74 is missing, its numbering skipping from 73 to 75. The missing folios were already gone when the manuscript was purchased in 1912, and the information is public, meaning the Vespers already knew. Amy reasons they were sent not to steal the manuscript but to identify what they need: folio 74.

Outside, a former assistant of Astrid's mentions a medievalist named Dr. LaCher Siffright who studied the Voynich alongside Astrid. Atticus realizes words his dying mother mumbled, which he mistook for "voyage," were actually "Voynich," spoken with Dr. Siffright's name. Among the hostages, Alistair Oh dies from a septic wound sustained during a failed escape. A Vesper video call delivers the news, and Vesper One reminds them they have 48 hours left.

Atticus and Jake access Astrid's email and crack coded messages from Dr. Siffright. The decoded text reads "IGUAZU VOY FALLS POOLS," pointing them to Iguazu Falls in Brazil. A postscript clue yields the number 74, confirming the connection to the missing folio.

In Brazil, Isabel Kabra orchestrates attacks on Atticus. At the falls, a man with a blowpipe targets Atticus; Jake shoves his brother aside, but Dan is struck by a curare-tipped dart and collapses, paralyzed. A doctor performs CPR until the poison wears off. Amy deciphers a cryptic warning delivered earlier by a street performer, realizing Isabel is behind the attacks and that a third attempt is coming.

A taxi driver recognizes Voynich illustrations on Dan's laptop and drives them to a thermal spa whose pools match the decoded message. Searching the patio, Dan finds a crack in the decking where Dr. Siffright confronts him, guarding the folio's hiding spot. Over dinner, she explains she found what she believes to be the missing folio in an Italian monastery and hid it here after experiencing break-ins and surveillance.

Before she can respond to Amy's request for the folio, a Vesper assassin hurls a knife at Atticus. Dr. Siffright throws herself in front of him and is gravely wounded. Before losing consciousness, she whispers to Dan, "You know," confirming the folio's location. That night, Amy retrieves the laminated folio from the crack. One side displays interlocking astronomical circles with triangular teeth: gears. Faint pencil markings read "ARCH" and "ANTIK," which Atticus identifies as references to Archimedes, the ancient Greek mathematician, and the Antikythera mechanism, an ancient astronomical computing device attributed to him.

Amy retreats into a detached, dissociative state, and Dan assumes leadership. He dispatches Jonah Wizard, a Cahill cousin, and Hamilton Holt, another ally, to Sicily, Archimedes' home, to investigate. Dan compares a Vesper location list with Isabel's charity destinations. Jake identifies the Vesper locations as subduction zones, geologically unstable areas prone to earthquakes, and five sites appear on both lists. Dan concludes Isabel is Vesper One, which brings him relief: It means his father, Arthur Trent, whom he feared might hold that role, is not.

In Sicily, Jonah and Hamilton find a lead in the Archimedes Palimpsest, a medieval prayer book written over scraped-off copies of Archimedes' works, now partially recoverable through modern imaging. Via Skype, the group examines a newly uncovered section containing gear diagrams matching folio 74 and a sketch of the Madrigal ring, a Cahill heirloom embedded in Amy's watch, entrusted to her by Grace. Atticus translates Latin fragments referencing magnets, the earth's crust, and subduction zones. The text names the device machina fini mundi: "machine for the end of the world." The Vespers have been systematically stealing components to assemble this doomsday device.

Vesper One orders them back to New York and demands Amy's Madrigal ring, calling it "the final piece." A video shows Nellie with a gun to her head. Amy, deep in dissociation, initially refuses, but Dan insists. At the drop in Central Park, a trained golden retriever takes the bag containing the ring and the folio. Amy is shattered: By surrendering the final piece, she has given the Vespers everything they need. She flees the hotel and vanishes into the streets.

Dan prepares the group to relocate to Attleboro. Alone, he removes a test tube of cloudy amber liquid from his backpack: the serum he secretly synthesized at a Columbia University lab. Resolved that no one else will die, he raises the tube, says, "Here we go, Dad. Cheers," and drinks it.