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Some equations were never meant to be solved.

When cryptic mathematical formulas begin appearing on government networks worldwide, decrypter Calla Cress recognizes a pattern that shouldn't exist, an 18th-century mathematical formula that perfectly predicts modern disasters. As rivers across Europe rise in perfect synchronicity, financial markets fluctuate with impossible precision, and weather systems align with mathematical certainty, one truth becomes clear: someone has unlocked "The Calculus."

Stolen from a British library's restricted section, the centuries-old manuscript contains a revolutionary mathematical framework that doesn't just predict catastrophes—it forecasts exactly how humanity will respond. In the wrong hands, it's the ultimate manipulation tool.

Racing against cascading global crises, Calla and her team—tech genius Jack, quantum computing expert Nash, and intelligence officer Marrees—must piece together the fragmented formula before reclusive data scientist Leonora Crisp can sell the complete predictions to the highest bidders. But with each solved equation, Calla discovers something even more disturbing: her own genetic connection to the mathematician who created The Calculus centuries ago.

As her cryptographic abilities evolve into something beyond explanation, Calla faces an impossible question: If mathematics can perfectly predict the future, does free will exist at all? And what does The Calculus reveal about the child she may one day have—referred to in the manuscript as "the perfect derivative"?

From the rain-slicked streets of Paris to the secure vaults of Zürich and the hidden archives of Munich, Calla must embrace her legacy as guardian of a mathematical secret that could save the world, or condemn it to a perfectly calculated destruction.

The Calculus Warning delivers heart-pounding suspense at the intersection of cutting-edge technology and ancient knowledge, where numbers don't just describe our world, they control it.

The Calla Cress Decrypter Thriller Series Reading 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 Falcon Syndrome

Book 10: The Queen of Sheba

Book 11: The Calculus Warning

Book 12: The Cobra Paradox

Book 13: The Room Of Martyrs

Book 14: The Eiger Mosaic

Book 15: Enemy of Wolves

Book 16: The Pharaoh's Mask

Find the Full series here.

Click here for the full reading guide.

Find the Full Series here.
Click here for the full reading guide.

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.

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