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Silver Gravity Books

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The Decrypter: The Eiger Mosaic: Rose Sandy, Calla Cress Decrypter Thriller Series, Book 14

Suspense, Thriller & suspense, Action & adventure, Technology, History, Arts, Business, Crime & mystery, Family, Fantasy, Horror, Sci-fi, Travel, Western, and Romance

Every Silver Gravity story centres women with agency.

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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.

Listen to the series here:

About the Calla Cress Decrypter Series

The Calla Cress Decrypter Series is a female-led action-adventure techno-thriller series that blends global espionage, cryptography, and high-stakes discovery.

Often compared to a female James Bond crossed with Indiana Jones, the series follows Calla Cress, a brilliant cryptographer and museum curator whose expertise in ancient manuscripts and hidden systems draws her into international conspiracies. As intelligence agencies, criminal networks, and secret organisations collide, Calla is forced to navigate a world where knowledge is power — and decoding the truth can destabilise nations.

Each book stands alone while contributing to a larger arc of global intrigue, making the series perfect for readers who enjoy smart, fast-paced thrillers led by a woman who survives on intellect, courage, and moral clarity rather than brute force alone.

What Kind of Thriller Is This?

This book is best described as a female-led action-adventure techno-thriller.

It combines:

Technothriller elements (cryptography, data, hidden systems, modern intelligence warfare)
Espionage and conspiracy involving governments and shadow organisations
Action-adventure storytelling across global locations
A smart female protagonist whose intelligence drives the plot

If you enjoy thrillers where ideas are as dangerous as weapons — and where discovery triggers global consequences — this series is designed for you.

If You Love James Bond or Indiana Jones…

Readers often compare this series to James Bond and Indiana Jones, but with a modern, female-led twist.

Like James Bond, the story features global stakes, intelligence agencies, and dangerous conspiracies.
Like Indiana Jones, it revolves around ancient knowledge, hidden artefacts, and discoveries that reshape history.

What sets Calla Cress apart is that intelligence is the primary weapon. Codes replace gadgets. Pattern recognition replaces brute force. And the heroine’s strength lies in insight, scepticism, and resolve.

Story Tropes & Reader Appeal

Is This Book for You?

Do I Need to Read the Series in Order?

Each Calla Cress novel is written to stand alone, with its own central mystery and resolution.

However, reading the series in order allows you to follow Calla’s evolving relationships, growing influence, and the wider conspiracy arc that unfolds across the books. New readers can start here, while returning readers will uncover deeper connections.

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

About Rose Sandy

Rose Sandy is an independent author and publisher known for writing female-led action-adventure and techno-thriller fiction.

She is the creator of the Calla Cress Decrypter Series, a globe-spanning techno-thriller series often compared to a female James Bond crossed with Indiana Jones. Her work blends cryptography, global conspiracy, and high-stakes discovery, with a focus on intelligent heroines who survive through insight, courage, and moral clarity.

Rose Sandy’s stories are characterised by fast-paced plots, international settings, and the collision of history, technology, and power. Her fiction is written for readers who enjoy smart thrillers with real-world stakes and strong female protagonists at the centre of the action.