The world has changed since the first time The Three Investigators went into action, but some things never go out of style. The persistence of truth. The power of perseverance. The importance of questioning everything. Conceived and co-written by Elizabeth Arthur, the daughter of Robert Arthur, the creator of the Three Investigators universe, this exciting reboot of the classic series takes its iconic characters into a new age. They return reimagined, reinvigorated, and more relevant than ever. In the seventh book of a 26-book story arc, the summer is beginning with an unusual challenge for The Three Investigators. At the end of the previous summer, Jupiter invited their new friend Mallory MacLeod to join the team as a Special Consultant. She's also been helping out at the Salvage Yard, so she, Jupiter, Pete, and Bob are all present when Uncle Titus returns from the Napa Valley with an intriguing artifact - a curious sandstone wheel. The wheel appears to be a grindstone, engraved with the birth and death dates of Galileo Galilei, the brilliant Italian inventor and astronomer with ties to the powerful Medici family. When Uncle Titus suggests the wheel could be connected to rumors of a hidden treasure, the team quickly shifts gears to investigate. They travel to the old Victorian "calendar house" where the wheel was found - a hotel owned by Portuguese immigrants who are unaware of the house's mysterious past. As it turns out, both the house and a nearby Franciscan monastery are brimming with Masonic symbols. The boys soon find themselves counting doors, rooms, and panes of glass, and deciphering cryptic letters in pigpen cipher that date back to 1890. When Mallory joins them and uncovers the startling connection between an ancient organization, the Illuminati, and the Masonic Order, the case takes on an added urgency. But the puzzle isn't adding up. Is the Italian stonemason, Clemente DeLuca, as innocent as he seems? Could the man writing a book about calendar houses be hiding his true intentions? Are the brown cotton robes the monks wear acting as a disguise for one of them? Locked inside the Tower Room, the team must work together to solve the mystery before it's too late. But the villains are closing in on the calendar house's secret - and they won't stop until it's theirs! Join Jupiter, Pete, Bob, and Mallory as they decode centuries-old secrets, face dangerous enemies, and reveal a long-hidden treasure in this intense new chapter of The Three Investigat