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The Decrypter: The Pythagoras Clause, The Calla Cress Decrypter Thriller Series, Book 5 - Rose Sandy
The Decrypter: The Pythagoras Clause, The Calla Cress Decrypter Thriller Series, Book 5 - Rose Sandy
Action & adventure, Suspense, Thriller & suspense, Technology, Crime & mystery, Romance, Sci-fi, and History
Book Number in Series
Book Number in Series
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Predicting the future was supposed to be a game – until it turned deadly.
When a seemingly harmless horoscope app begins correctly predicting events and leaves its users in deep comas, codebreaker Calla Cress is thrown back into the world of spies and secrets. The app issues a chilling warning about her own fate and triggers an old nemesis to resurrect a lost technology built by a student of Pythagoras. With the help of her team, she must decode the mathematical clause embedded in the app’s code, revisit painful memories and race across continents, before the algorithm makes one final prediction that will erase free will.
You download the app. It predicts your future. Then you never wake up.
British Museum curator turned secret agent Calla Cress didn’t want to know the future. Heck, the future can wait, but not when it’s wiped clean her present.
The Decrypter and The Pythagoras Clause pits museum curator and secret agent Calla Cress against her most personal and mind‑bending adversary yet. When a horoscope app starts predicting real events and sending its users into comas, Calla’s own life is threatened by a prophecy she can’t ignore. To stop the crisis, she must unravel a Pythagorean algorithm embedded in the app—one that has roots in ancient Greece and ties to her own genetic engineering.
From the bazaars of Istanbul to the old streets of Havana, she decrypts centuries‑old ciphers while evading a ruthless tech magnate bent on mastering destiny. This heart‑pounding techno‑thriller blends cryptography, artificial intelligence and historical intrigue into a story about the cost of knowing the future. With vivid settings, relentless action and ethical quandaries, it delivers the perfect blend of high‑octane suspense and thought‑provoking speculation.
Get ready for a wild ride of non-stop action and suspense with this thriller, perfect for fans of Steve Berry, Scott Mariani, Ernest Dempsey, and Clive Cussler.
Reader Praise
“Predicting the future was supposed to be a game, until it became deadly serious. This thriller will have you flipping pages into the night.”
“An exhilarating cyber‑thriller packed with history, codes and action from Turkey to Havana. Fans of Dan Brown, Scott Mariani and Clive Cussler will love it”
Locations & interesting places in the book
- Masai Mara, Kenya: A wildlife reserve where Calla and Jack climb a disguised transmitter mast to stop a biohack.
- Hannam‑Dong UN Village, Seoul: Home of Chun‑Hei Tam; illustrates the everyday impact of the Scope app.
- Istanbul, Turkey: Historic mosques and markets hide clues to the Pythagoras Clause; the city’s blend of East and West adds atmosphere to the hunt.
- Havana, Cuba: Colonial architecture and revolutionary forts hold carvings of the Clause; the sultry climate contrasts with the precision of mathematics.
- UK Space Agency Research Center, Swindon: Site of the prologue where Nicole meets Andor Heskin and sets events in motion.
- Caribbean research facility: A secret island lab where comatose victims are connected to servers running the Clause algorithm; the climactic showdown occurs here.
- London: Calla’s base of operations at the British Museum; serves as a hub for research and planning.
Listen to the series here:
ABOUT THE SERIES
ABOUT THE SERIES
Calla Cress is no ordinary museum curator. By day, she manages ancient manuscripts, Byzantine relics, and rare artifacts at the British Museum. But in the shadows, she’s a top operative, for a covert multi-government spy agency. With unparalleled skills in cryptography, ancient languages, and digital intelligence, Calla is known as The Decrypter,the one they call when the stakes are global and the clues are buried deep in history.
The Calla Cress Technothriller Series
Introduction: The Curator and the Code
Calla Cress is a brilliant curator at the British Museum, a woman whose unparalleled command of history and ancient languages has made her a luminary in the academic world. Her quiet life shatters when she’s recruited to decipher a cryptic, long-lost manuscript written in an apparently unbreakable code. The secrets locked inside are no mere curiosities: they map the location of resources that could make crude oil look obsolete. Thrust from scholarly halls into the shadows of global espionage, Calla learns that priceless artefacts can be triggers for future wars—and her first mission is only the beginning.
The Scope of the Conspiracy: A Global Race Against Time
What starts with a single manuscript escalates into a worldwide battle against a cascade of interlinked threats. The Calla Cress series blends historical mystery, high-stakes international espionage, and cutting-edge technothriller energy. From London and Paris to the deserts of Morocco and the jungles of the Congo, Calla and her allies piece together clues centuries in the making. Hunted at every turn by relentless foes—wielding carbonado diamonds and moving like computer-augmented phantoms—they bend physics and technology to their will. With each book, the stakes rise and the pace accelerates, as Calla uncovers a conspiracy vast enough to bring the world to its knees.
A Promise to the Reader: Unforgettable Adventure
Expect an action-packed ride from first page to last—breathless momentum with brains and heart. Each instalment delivers intricate mystery, breathtaking suspense, and relentless thrills. If you love globe-trotting puzzles, fierce heroines, and technothrillers that never let up, the Calla Cress series belongs on your shelf.
Main Characters
Calla Cress—the series protagonist—is a British Museum curator and ISTF agent on a personal crusade to uncover her origins and the truth behind her genetically enhanced abilities. Facing cryptic codes and dangerous foes, her journey pushes her cyber-espionage skills to the limit. Across the series she evolves into a formidable operative, determined to reconcile the mysteries of her past with her present while battling adversaries who weaponise her own secrets against her.
Jack Kleve is the quintessential ally—a visionary tech entrepreneur and ISTF operative who lends his skills to Calla Cress and Nash Shields. While navigating corporate rivalry and the murky ethics of rapid technological advancement, his arc bends towards recognising the greater good over profit. Jack’s devotion to Calla adds a personal dimension to his conflicts, intertwining the professional with the emotional. His shift from profit-driven inventor to socially conscious partner marks a pivotal transformation in the series.
Nash Shields, an NSA and ISTF agent, is the steadfast protector and love interest, driven by a profound sense of duty. He confronts formidable enemies and complex political networks while safeguarding vital technologies alongside Calla. His journey forces him to question the ethics of his mission, balancing loyalty to his agencies with a deepening moral awareness. Torn between professional duty and personal feelings, Nash walks a precarious line between love and allegiance.
SERIES READING ORDER
SERIES READING ORDER
The Calla Cress Decrypter Thriller Series In Order
- Book 1: Secret of the Lost Manuscript
- Book 2: The Mind Hacker
- Book 3: Digital Eyes Only
- Book 4: The Storm’s Eye
- Book 5: The Pythagoras Clause
- Book 6: The Beale Ciphers
- Book 7: Atlantis of the Sands
- Book 8: Kingdom of Diamonds
- Book 9: The Falcom Syndrome
- Book 10: The Queen of Sheba
- Book 11: The Calculus Warning
- Book 12: The Cobra Paradox
- Book 13: Room of Martyrs
- Book 14: Eiger Mosaic
- Book 15: Enemy of Wolves
- Book 16: The Pharaoh's Mask
- Book 17: The Eternity Hypothesis
- Book 18: The Sculptor's Code
- Book 19: The Solomon Agenda
- Book 20: The Pheonix Cipher
- Book 21: The Cairo Key
- Book 22: Red Fox Agenda
- Book 23: Phaistos Disc
- Book 24: Scorpion Gold
READ A SAMPLE
READ A SAMPLE
Pythagoras App Book Sample.
Meet the Author
Meet the Author
Meet the Author Rose Sandy
Rose Sandy writes adventure thrillers that blend espionage, technology, and history into fast-paced adventures. Her stories dive into the world of covert intelligence, scientific breakthroughs, and global conspiracies, perfect for readers who love suspense with a twist of "what if?" Whether you're on a morning commute or relaxing on a Sunday, her books promise to entertain, surprise, and transport you to hidden corners of the world.
A true globetrotter and lifelong communicator, Rose draws inspiration from historical archives, cutting-edge tech, and conversations with intelligence insiders. When she's not researching in the British Library or exploring Churchill’s War Rooms, she’s crafting thrillers that weave intrigue, action, and a hint of romance. Discover more here or join her newsletter at subscribepage.io/Wuqko4.
Tropes You'll Love
Tropes You'll Love
predictive horoscope app, technothriller novel, AI prophecy thriller, Calla Cress codebreaker, cyber espionage book, science fiction suspense, ancient mathematics mystery, global conspiracy thriller, female spy hero, data privacy novel, Black Mirror fans, techno suspense, Rose Sandy new release, international action adventure, mind control app, secret society thriller
Audio Book Sample
Audio Book Sample
Audio book in production.
Other Book Details
Other Book Details
Technothriller, Science Fiction, Cyberpunk, Action Adventure, Thriller, Spy Fiction, Conspiracy Thriller, Predictive AI, Ancient Mystery, Women’s Adventure, Data Privacy
FAQs
FAQs
Another hit for Rose Sandy, the 5th book in the series and probably the best yet, keep it up Rose I highly recommend this book.
A well researched and written book. Rose has "Been and seen". As someone who has also visited and seen many of the places vividly described, I can also say "Thanks for the memories" : I have had knives and guns pulled on me and walked past unexploded devices et cetera so I can relate to the excellent descriptive writing and hope that there will be many more books to come. Enjoy.
Another excellent Calla Cress adventure, gripping excitement to the end. Great read, would recommend it to anyone.
As we have come to expect from this author this is a well written fast-paced blockbuster of a book, brilliant storyline amazing characters with twists and turns to keep you turning pages till the wee small hours. I can't recommend this book highly enough an outstanding story, can't wait for the next one, Baz.
The thriller series that keeps on giving. Once again the story keeps you gripped from start to finish. Read as apart of a series but could be read as a stand alone book although some of the background info would be missing then. Like that there is lots to think about not just in the story line but the thought patterns from the wealth of information given
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