M.B. Courtenay’s A Spy Inside the Castle is an ambitious debut that thrusts readers into the murky crossroads of global intelligence, political intrigue, and emerging artificial intelligence. The first instalment of a planned series featuring security analyst–turned–reluctant operative Ethan Briar, Courtenay wastes no time establishing a world where power is hoarded, truth is elusive, and the line between foresight and manipulation grows perilously thin.

Ethan Briar is a security analyst and keynote speaker at the Global Risk Summit hosted by his employer, SOVERINT, a private intelligence company ‘where powerful men outsourced their most delicate problems to those willing to solve them in the shadows.’ Ethan is considered somewhat of an oracle within the intelligence community, offering astute predictions about global political and economic systems. However, when the German Chancellor is assassinated after he makes a dire prediction about the future of Germany, he is unwillingly drawn into a covert operation to uncover a mole leaking government intelligence secrets.

Thus, the reader is plunged into a complex and confusing world of global intelligence and politics with numerous power players and hidden agendas. What follows is a layered and often disorienting journey – one that challenges the reader’s assumptions as much as it does its protagonist’s – and sets the stage for a thriller series rooted in complexity, ambiguity, and the shadowy forces shaping the modern world.

A key component of the plot is ARCLIGHT, a powerful AI with extraordinary capabilities for forecasting the future. Hidden deep within Castle Martin Manor on Scotland’s remote Isle of Skye, it becomes Ethan’s ultimate destination as he pursues his target, FOXGLOVE, racing to uncover her identity before his own mission is exposed.

Courtenay has crafted an intricate work of many threads that ultimately come together to make sense as a coherent whole. The reader must be patient though, working through the initial disorientation that comes from the many shifts in time, place and perspective. The reader also needs to be willing to suspend disbelief in those sequences in which Ethan is taken into ARCLIGHT and shown simulations of not just future scenarios, but also the past and of the origins of long-standing organisations destined to pursue global power and dominance.

A strength of the novel is Courtenay’s writing style, which remains engaging even when the plot borders on the implausible. Whether it stretches credulity too far or is alternatively bold and ambitious with a large scale to distinguish it from conventional spy thrillers will be up to the reader. Readers willing to navigate its complexity will find themselves rewarded with momentum building to a finale that cohesively neatly ties together its many threads and establishes a clear direction for future instalments of a new franchise in the genre.

A Spy in the Castle will be released December 6 2025. We Need to Talk About Books was supplied with an advanced copy in return for an independent review.