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The Lost Key

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A stolen key. A silent war. One man caught in the crosshairs of both.

When a piece of classified code vanishes from GCHQ, London doesn’t hear an explosion. It feels a silence.

The file is nicknamed the Lost Key—a powerful cryptographic tool capable of quietly unlocking secure systems across the West. Whoever controls it can rewrite financial records, crash infrastructure, and turn trusted networks into weapons.

Former SAS operator James O’Neill thought he’d left that world behind. Now working as a security consultant, he’s dragged back into the shadows when an old contact in MI5 slips him a the Lost Key is on the move, bodies are starting to fall, and his name is suddenly appearing in the wrong briefings.

From back alleys in Belfast to anonymous server farms outside Warsaw, James is forced to track a threat that moves at the speed of data and kills without leaving fingerprints. A ruthless Belfast crime boss, a compromised insider inside the British state, and a faceless group of foreign operators all want the same thing—and they all think James is in their way.

As the digital trail twists into a very human conspiracy, James has to decide who he can trust, what he’s willing to sacrifice, and how far he’ll go to stop a weapon that doesn’t fire bullets… it erases truth.

If he fails, the first thing to disappear will be the evidence that he ever tried.

The Lost Key is a high-velocity British espionage thriller that blends boots-on-the-ground tradecraft with modern cyber warfare and political intrigue.

Perfect for readers who

Relentless pacing and grounded action

Ex-military protagonists with a moral code and a past that won’t stay buried

Intelligence agencies, covert operations, and shadow wars in Europe

Tech-driven cyber weapons, compromised networks, and weaponised data

The feel of Lee Child, Tom Clancy, and Mark Greaney in a modern British setting



Start The Lost Key today and step into a world where the most dangerous weapon on earth fits on a single drive and everyone is already at war for it.

318 pages, Paperback

Published December 3, 2025

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2 people want to read

About the author

James O'Neill

1 book3 followers
James O’Neill writes the kind of missions he once ran.

A former British Special Forces operator with nearly two decades in the shadows, he has planned and executed operations across Europe, the Middle East, and beyond. Now he channels that experience into high-impact espionage thrillers that fuse boots-on-the-ground tradecraft with the cold logic of modern cyber warfare.

His debut novel, The Lost Key, launches the James O’Neill thriller series: a hard-edged, British-driven blend of special operations, intelligence intrigue, and high-stakes geopolitics aimed squarely at fans of Lee Child, Tom Clancy, and Mark Greaney. Expect lean prose, moral ambiguity, and operations where every decision has a cost.

When he is not writing, O’Neill works internationally in risk, security, and technology, staying close to the real-world threats that shape his fiction. He lives in the United Kingdom and is currently at work on the next James O’Neill thriller.

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Displaying 1 - 19 of 19 reviews
Profile Image for Abhay Singh.
1,064 reviews75 followers
December 12, 2025

⚫️The Lost Key by James O'Neill is an exhilarating mix of classic espionage tension and cutting-edge cyber warfare a novel that grabs you from the very first page and doesn’t let go. James O'Neill crafts a thriller so tightly woven and fast-paced that with every chapter, you feel like you’re diving deeper into a world where silence can be more perilous than gunfire.

⚫️The premise is electrifying: the Lost Key is a stolen cryptographic tool that can quietly dismantle the digital foundations of our world banking systems, communication networks, national security. But what truly sets this story apart is how James O'Neill creates an atmosphere of creeping dread. There are no dramatic explosions to signal danger… just a chilling awareness that the world is shifting in ways most people will never notice.

⚫️At the center of it all is James O'Neill, a former SAS operator who yearns for a normal life but finds himself pulled back into the shadows. He’s a remarkably relatable hero skilled yet scarred, decisive yet haunted by a past that lingers. The moral complexity and grit of his character make him instantly engaging, especially as he navigates the secrets of MI5, foreign operatives, and a ruthless crime syndicate in Belfast.

⚫️James O'Neill's writing shines brightest when he combines real-world tradecraft with cyber stakes that feel breathtakingly real. The chase flows seamlessly from the winding, dimly lit streets of Belfast to high-security data centers in Warsaw, each location vividly brought to life. The threat feels alarmingly tangible, and the tension is amplified by the terrifying reality of a world where a weapon that erases truth is far more dangerous than one that fires bullets.

Fans of Lee Child, Tom Clancy, and Mark Greaney will find themselves right at home with The Lost Key.

Happy reading ❤️✨
Profile Image for Eliza Rose.
36 reviews2 followers
Read
January 29, 2026
The Lost Key is a sharp, modern espionage thriller that blends classic tradecraft with the terrifying realities of cyber warfare. The premise is chillingly plausible: a single stolen cryptographic weapon capable of quietly dismantling governments, economies, and trust itself.

James O’Neill is a compelling protagonist, a former SAS operator pulled back into a conflict where bullets matter less than data, and loyalty is harder to define than ever. The novel moves confidently from Belfast’s criminal underworld to Europe’s shadowy intelligence corridors, maintaining relentless pacing while grounding the stakes in human cost and moral consequence.

What elevates The Lost Key is its balance between action and intelligence realism. This is not just a chase thriller; it’s a story about erasure, manipulation, and how modern wars are fought silently. Fans of Lee Child, Tom Clancy, and Mark Greaney will feel right at home, but the cyber angle gives this story a distinctly contemporary edge
Profile Image for James O'Neill.
Author 1 book3 followers
Read
January 10, 2026
I’m the author, so this isn’t a traditional review. I’m proud of The Lost Key as a debut, especially the pacing from the mid-point onwards and the mix of tradecraft and tech. If you enjoy Tom Clancy / Mark Greaney style thrillers, I hope it lands as a solid 4-star read for you and I’d value your honest rating more than mine.
Profile Image for Hammilton Judy.
1 review
January 31, 2026
The Lost Key by James O’Neill is a very exciting spy thriller that mixes field operations with political and intelligence drama in a really strong way. It is one of the most engaging thrillers I’ve read recently. The story starts with a tense opening scene at GCHQ where a data system alert suddenly turns serious. An analyst named Eleanor Shaw notices that someone is secretly accessing restricted intelligence files using fake maintenance credentials. She tries to log the incident, but her report disappears after the system resets, which shows that the breach goes deeper than it first appears.

At the same time, the thief disguised as a maintenance worker copies sensitive data onto a USB drive and escapes in a van. The tracking signal shows the data moving toward Northern Ireland, which sets the main conflict in motion. The story then shifts to James O’Neill, a retired operative living quietly in Scotland. His peaceful life is interrupted when Sarah Sterling contacts him about the stolen data drive, explaining that it could be extremely dangerous if foreign agents use it. O’Neill reacts calmly and professionally. He prepares his gear, removes digital traces, and plans his next moves carefully. I liked how the book shows his thinking process instead of making him act recklessly.

The London briefing scenes explain how the breach happened and why the missing drive is such a big threat. The device was originally a powerful access tool, and in the wrong hands it could expose vulnerabilities and identities. Sarah recruits O’Neill for a mission that is unofficial and risky because government bureaucracy is slowing down the response. From there, the Belfast operations become a major part of the story. O’Neill builds a safehouse, works with Mick Donnelly, and runs dock surveillance. The investigation details like container irregularities and driver behavior make the story feel realistic and well researched.

The plot keeps growing with more players joining, including Mac, and with the villain Orlov directing operations from Dublin while larger plans are coordinated from Moscow. There are also internal investigations happening in London as Sarah tries to track leaks inside the system. The mix of field missions, cyber threats, and internal politics keeps the tension high. The later sections involving transport routes and the Shadow Key network raise the stakes even more and lead to a strong, action filled climax. Even the ending suggests that the danger is not fully over, which fits the spy genre well.

I also want to praise the writing quality. The book is very clean and well edited, and the action is easy to follow without feeling oversimplified. The author clearly understands spycraft and intelligence procedures, which makes the story feel authentic instead of exaggerated. Overall, I think this is a very strong thriller, especially for readers who enjoy realistic espionage stories. I would definitely recommend it to anyone who likes modern spy novels.
Profile Image for World Of.
161 reviews19 followers
December 17, 2025
The Lost Key is a sharp, high-stakes espionage thriller that plunges readers into a modern battlefield where silence is more dangerous than gunfire and data is the deadliest weapon of all. From its opening pages, the novel establishes an atmosphere of tension and urgency, proving that in the world of intelligence, the absence of noise can signal the greatest threat.

At the center of the story is James O’Neill, a former SAS operator turned security consultant whose attempt at a quieter life is violently interrupted. He is a classic but compelling thriller protagonist—highly skilled, morally grounded, and haunted by a past that refuses to stay buried. As his name begins to surface in the wrong intelligence briefings, O’Neill is forced back into a shadow war where trust is scarce and survival depends on reading both people and systems correctly.

The plot revolves around the Lost Key, a stolen cryptographic weapon capable of dismantling governments without firing a single shot. The concept feels chillingly plausible, and the author skillfully blends cyber warfare with traditional espionage tradecraft. From the streets of Belfast to remote server farms in Eastern Europe, the narrative moves at a relentless pace, maintaining suspense while steadily escalating the stakes.

What sets The Lost Key apart is its balance between technical intrigue and human conflict. Alongside compromised insiders, foreign operators, and criminal power brokers, the story explores the personal cost of secrecy and sacrifice. The digital trail may be complex, but the motivations driving the characters remain sharply human—greed, loyalty, fear, and the desire to control the truth.
Profile Image for Sarah Banks.
18 reviews
January 31, 2026
When i picked up this book to read, i wasn’t quite sure what to expect but i’m glad i read it, every page of this story feels alive with tension. The moment the Pelican is stolen, the clock starts ticking. You can feel every danger: surveillance, traps, enemy agents. Sarah Sterling is amazing because she doesn’t just fight with guns; she fights with brains, plans, and clever tricks. James and his team are experts in stealth and survival, and every move they make in Ireland shows careful skill and courage. Falcon Stage is like watching a perfect chess game, where each player moves pieces, sets traps, and predicts the enemy’s reactions. The story is full of moments where you hold your breath, from roadside encounters to political leaks in London. Even small details, like burner phones or fake news feeds, make the story feel real and thrilling. By the end, the reader feels like they have been part of a dangerous, clever, and exciting spy mission.
This has the makings of a great series. I’m in.
Profile Image for Emma Potter.
4 reviews
February 1, 2026
Espionage Told Through Strategy Rather Than Spectacle

What makes this book exceptional is its refusal to rely on flashy action alone. Instead, it builds suspense through intelligence work that feels real and earned. The planning sessions in London are just as gripping as the movements through County Clare. Sarah’s decisions are driven by consequence, not ego, and her awareness of internal betrayal makes every choice dangerous. James’s field operations show discipline and restraint, especially in moments where violence could create the wrong narrative. Falcon Stage unfolds as a coordinated effort across multiple levels: local gangs, contractors, political media pressure, and intelligence manipulation. Orlov and Reznikov are frightening not because they are loud villains, but because they are patient and methodical. The book understands that espionage is about control of momentum, not domination. The final chapters leave the reader with a sense that victory is temporary, fragile, and costly, which makes the story feel honest and mature.
Profile Image for Hailey Jones.
18 reviews
February 1, 2026
A Deeply Human Story Hidden Inside a Global Intelligence Crisis

Beneath the layers of strategy and politics, this book tells a deeply human story. Sarah Sterling carries the weight of responsibility alone, fully aware that doing the right thing may destroy her career. James and his team operate with quiet loyalty, bound by trust rather than orders. The Irish countryside becomes more than a setting; it becomes a place where exhaustion, fear, and resolve are tested step by step. Falcon Stage amplifies pressure on everyone involved, forcing characters to reveal who they really are. Hume’s actions show how fear of exposure can be more dangerous than foreign enemies. Orlov’s cold calculations contrast sharply with the personal risks taken by those on the ground. Even the smallest moments , sharing coffee, waiting in silence, choosing not to act, carry emotional weight. By the end, the story feels less like a mission report and more like a record of people surviving a system designed to comsume them.
Profile Image for Dwayne Collins.
1 review
January 31, 2026
This story is an amazing journey into the world of spies and secret missions. From the very first theft at GCHQ to the final chase in Ireland, every part of the story keeps you on edge. Sarah Sterling is a strong and clever heroine who always thinks several steps ahead, using her mind to protect important secrets. James, Mac, and Mick are perfect partners in the field. Watching them move quietly through hedgerows and dodge enemy patrols is exciting and realistic. Falcon Stage shows how smart planning, fake routes, and careful manipulation of locals can create huge effects without open battles. Orlov and Reznikov are terrifying in how smart and patient they are, making every step dangerous. The story also shows the human side of espionage: the stress, the choices, and the friendships that keep people alive. The ending, with the Pelican safe and the Ghost Channel alive, leaves you thrilled and satisfied. This is one of the most exciting and smart spy stories you can read.
Profile Image for Nick Lambert.
3 reviews
February 1, 2026
A Modern Spy Novel That Respects the Reader’s Intelligence

This book trusts the reader to follow complex operations without simplifying them. It does not explain everything twice, nor does it rely on convenient coincidences. The intelligence tradecraft feels researched and authentic, from burner phones and false satellite feeds to deniable contractors and local intermediaries. Sarah Sterling is written as a professional who earns respect through competence, not dramatic speeches. James’s field work is quiet, efficient, and realistic, showing how survival depends on discipline rather than heroics. Falcon Stage stands out as a turning point where multiple storylines converge naturally. The Ghost Channel epilogue is subtle but powerful, suggesting continuity rather than closure. This is a story that rewards attention and patience, offering a layered experience that grows stronger the more carefully it is read.
7 reviews1 follower
January 8, 2026
The Lost Key is an electrifying modern spy thriller that quickly draws you into its captivating world. James O’Neill masterfully maintains a breakneck pace while still delivering depth and realism. The cyber warfare aspect is not only chillingly believable but also feels refreshingly relevant. Our protagonist, James, an ex-SAS operative, is complex, flawed, and guided by a strong sense of morality. The European backdrops enhance the story, adding authenticity and tension at every twist and turn. This is espionage at its finest smart, grounded, and razor-sharp. The stakes rise steadily, keeping the suspense tight right up to the last page. If you’re a fan of clever, high-octane thrillers, you’ll find it nearly impossible to put this one down.
Profile Image for Joseph Rankine.
2 reviews
January 31, 2026
This story shows how intelligence missions work in a very realistic way. The planning, the technology, the movement of teams, and the political consequences all feel authentic. Sarah Sterling is amazing because she can think ahead, outsmart enemies, and handle dangerous situations calmly. James, Mac, and Mick are experts in fieldwork, moving quietly and efficiently through Ireland. Falcon Stage is brilliantly designed: it mixes strategy, diversion, and local help to control every outcome. Orlov and Reznikov make the story tense because they are patient and intelligent villains. Even small characters, like Kavanagh or ferrymen, add depth. The story combines intelligence, suspense, action, and politics in a way that is exciting but believable.
35 reviews1 follower
January 8, 2026
From the very first chapter, The Lost Key grabs your attention with a quiet intensity rather than loud explosions and it does so brilliantly. The idea of a weaponized piece of code is both chilling and incredibly believable. James O’Neill masterfully balances action and strategy, showcasing impressive control throughout. The protagonist feels relatable and human, not some untouchable hero, which really amps up the tension. The political intrigue is subtle yet impactful, never overshadowing the story. Each chapter builds urgency without any unnecessary fluff. The writing is sharp, confident, and has a cinematic quality to it. It’s truly a standout espionage thriller for our digital age.
9 reviews1 follower
January 8, 2026
If you're a fan of smart thrillers, this book is an absolute must-read. The way it combines cyber threats with classic spy craft feels both seamless and refreshing. James O’Neill really gets how modern wars are waged in the shadows and through data streams. The plot races along, but it never feels hurried or confusing. Each character has a role to play, and every scene is meaningful. The moral dilemmas add emotional depth that goes beyond just the action. This isn’t merely a chase; it’s a fight for the very essence of truth. A remarkable debut that confidently holds its own among the giants of the genre.
14 reviews2 followers
January 8, 2026
The Lost Key is one of those thrillers that sticks with you long after you’ve turned the last page. The notion that data could wipe out reality is both chilling and fascinating. James O’Neill builds tension through cleverness rather than relying on over-the-top violence. The pacing is unyielding, yet the narrative stays relatable and believable. Set against a backdrop of European espionage, the story feels rich and authentic. James, the main character, comes across as someone who truly embodies the life he narrates. The stakes are not just global; they hit home on a personal level too. It’s a polished, captivating read from beginning to end.
Profile Image for Chloe Lambert.
12 reviews
January 31, 2026
Solid start to what promises to be a gritty espionage series. The GCHQ theft scene is expertly paced: you feel the quiet panic as Eleanor realizes she’s watching an insider breach unfold in real time. The maintenance-uniform thief is chillingly professional; looped cameras, no serial on the drive, exit through a disabled fire door. James O’Neill’s Highland isolation is beautifully drawn; you can almost smell the rain and pine. Sarah’s phone call is all business, no warmth, which makes the stakes feel immediate. Only complaint: I want the next 198 pages now. I highly recommend for fans of slow-burn British spy fiction.
8 reviews1 follower
January 8, 2026
This book delivers exactly what a top-tier espionage thriller should.
James O’Neill writes with authority, clarity, and purpose.
The cyber warfare elements are realistic without becoming overly technical.
Action scenes are sharp, tense, and meaningful not just noise.
The story explores trust, betrayal, and sacrifice in a believable way.
The antagonist forces are shadowy, dangerous, and unsettlingly real.
Each chapter pushes the narrative forward with precision.
A smart, modern thriller that deserves serious attention.
Profile Image for Steven H.
5 reviews1 follower
January 19, 2026
So, I know the author but having read the book I can honestly say it a good book. First book and can’t wait for the next book.

If you enjoy great military thrillers with trade craft then this one is one you need to add to your list.

I would love to give it 5 stars but given I know the author I best not.. Sorry.
Profile Image for Beverly Cole.
2 reviews
January 31, 2026
This is one of the strongest openings I’ve read in a thriller in years. The prologue at GCHQ feels so real; the hum of servers, the amber-to-red alert climb, Eleanor Shaw’s growing panic, the thief calmly overriding certificates and slipping out with the USB in a lead-lined pouch. Then we meet James O’Neill in his stark Scottish cottage, a man who has deliberately erased his past, only to be dragged back by Sarah Sterling’s cold, urgent call. The prose is clean, economical, and tense. No wasted words. If the rest of the book keeps this level of atmosphere and tradecraft detail, James O’Neill is going to be a name to watch.
Displaying 1 - 19 of 19 reviews

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