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Some mountains guard deadly secrets. Some secrets change the world.

When satellite images reveal a mysterious mosaic carved into the treacherous north face of the Eiger, cryptographer Calla Cress recognizes what others cannot—a complex cipher hidden in plain sight for over seventy years. But what begins as a historical puzzle quickly escalates into a desperate race that could reshape the balance of global power.

The Alpine Cipher, a legendary WWII encryption key, was thought lost forever. Now it's resurfacing, along with technology decades ahead of its time. As Calla's connection to the mountain grows strangely stronger with each discovery, she's plagued by visions and memories that aren't her own—visions involving her long-missing parents on these very slopes.

With a catastrophic winter storm approaching, Calla must confront her lifelong fear of heights and join forces with elite operative Nash Shields and tech genius Jack Kleve to scale the Eiger's deadly north face. But they aren't climbing alone. Dr. Ingrid Wolff, a brilliant cryptanalyst with powerful backers, leads a team of mercenaries up the mountain with orders to secure the cipher by any means necessary.

As they ascend higher, Calla uncovers a stunning truth: the Alpine Cipher isn't just about buried wartime secrets—it's about the future of humanity itself. And somehow, her own genetic heritage lies at the heart of its mystery.

What her parents died protecting, she now must find. What others would kill to possess, she must understand. What was carved in stone and ice, she alone can decode.

From the breathtaking peaks of the Swiss Alps to hidden WWII bunkers beneath the ice, EIGER MOSAIC delivers heart-stopping action, ancient mysteries, and cutting-edge science in an explosive cocktail that will keep you turning pages late into the night. Perfect for fans of James Rollins, Steve Berry, and Dan Brown.

The truth is buried deep. The climb could be deadly. The cipher will change everything.

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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