Book Review: A Spy Inside the Castle by M.B. Courtenay

A Spy Inside the Castle, the first book in the Ethan Briar series, is a complex spy thriller that centers on Ethan, a disgraced former foreign service officer who is secretly recruited into the Nightshade Program at Castlemartin.

Once inside this classified US black site, Ethan becomes an elite private intelligence officer with a unique mission: find the mole and flush him out.

At first, the story seems to follow a straightforward, almost Le Carré-esque formula, which is classic spy game, cloak-and-dagger stuff. But then, the high-tech elements come in: Arclight, a quantum-seeded AI with uncanny predictive powers (basically the world’s first true “super intelligence”), and Ethan’s own “pattern clarity,” which is his uncanny ability to see hidden connections, a “superpower’ gained after a previous serious illness.

This ability gave him the ticket to entering this place that will turn his life entirely upside down. Suddenly, the novel isn’t just a spy thriller, but it soon becomes a high-staked techno-tech thriller. As much as I love classic espionage tales, I do love techno-thrillers more, so I was hooked.

The expected mission is to unmask the mole, codename Foxglove. However, it all goes wrong when Ethan’s handler, Jill Blackfeather, issues a chilling new order: kill Foxglove. This twist forces Ethan to confront both his own nature and the question of is what he is doing right. Is Foxglove really the traitor, and could Ethan actually go through with killing her?

Suddenly, his gift for pattern recognition isn’t just a superpower but a source of tension, which now clashes with his gut instincts and his sense of morality.

Early on, Ethan was merely just trying to earn recognition and validation from the system that eventually let him down. He’s shaped by a traumatic past that left him with his unusual abilities but also set him on a lonely path. As the story unfolds, his journey takes a turn toward self-discovery, allowing him to see the layers of betrayal from the very people and institutions he longed to gain access to.

Ultimately, this leads him to challenge not just the mole but the very superintelligence that is being used by those in power wanting to tighten their grip on the world, regardless of the consequences for ordinary people.

Ethan’s transformation is one of the novel’s biggest strengths: he becomes so much more human. There’s even a romantic thread running quietly through the story. While nothing overtly happens, there is real tension and chemistry in the scenes with a key character, which heads toward an open ending that hints at a possible HEA (“happily ever after,” for the romance folk).

Now, I’ll admit, I was a bit confused at times by the alphabet soup of various groups and secret projects: Arclight, Castlemartin, Project Nightshade, Der Kreis, Soverint…initially I found it lot to keep track of. Eventually, it does all tie together, however.

For anyone else feeling overwhelmed while reading, here’s a quick cheat sheet without major spoilers for the end of the novel: all these groups are interconnected parts of a global spy war under the umbrella of something called Labyrinth.

There are two main camps. Project Nightshade is the US intelligence project at Castlemartin (a CIA black site on the Isle of Skye in Scotland), and their so-called “crown jewel” is Arclight, the superintelligent AI. On the other side is Der Kreis (“The Circle”), which is a shadowy, European supremacist group hellbent on seizing Arclight’s secrets to destabilize the world order, including collapsing NATO, assassinations of key leaders, and creating global chaos. Soverint, meanwhile, is the corporate front Ethan uses to infiltrate Castlemartin.

While the secret programs, the world-threatening AIs, and the layers of conspiracy aren’t brand new to the genre, the author makes it all feel fresh. There is a chillingly plausible world here with betrayals, conspiracies, power grabs, and murder that is lurking around every corner with the fate of the world (not to mention Ethan’s own soul) hanging in the balance. Once I figured out who’s who, the plot became quite easy to follow.

As a real page-turner spy thriller with high-tech elements, it is a promising start of a great series.