After a disastrous operation six years ago, a disillusioned Alec Milius left MI6 and has been living under the radar ever since. He believes that both MI6 and the CIA, who figured in his last op, are looking for him, so he employs all the counter-surveillance techniques he learned as a spy: multiple phones, multiple email accounts, always on the watch for a tail. He's landed in Madrid where he's built a new life for himself, working for a banker, Julian Church, whose wife is Alec's mistress.

This life is thrown into disarray by two occurrences: a visit by an old friend from England—his first contact with anyone from his past—and a job Julian sets him. Alec's careful attention edges into paranoia as he wonders if Saul's visit is actually an attempt by MI6 to entrap him. Perhaps even Julian is out to get him, sending him to San Sebastián to interview Basque separatist Mikel Arenaza and report on the current stability of that part of Spain. Alec likes Mikel, and they plan to meet later in Madrid, but Mikel disappears en route. Caught up in Basque politics, unsure whom to trust, not even sure if he can trust himself, Alec tries to find out what happened to Mikel.

This, for me, is the best type of spy novel, the kind that tests my brain. Intelligent and surprising, it is not an adrenaline-fueled race to the finish, though suspense does build through the book. The characters, men and women, major and minor, are well-drawn. Alec, himself, is not someone I would want to know, but his honesty about his faults is enough to put me on his side. And there's also the integrity in him, twisted perhaps by his past, and the possibility of redemption. Adding to his appeal is his predicament as a loner, working outside the system, like so many of Le Carré's spies.

I loved the descriptions of life in Madrid, recognising many places and customs from my visits. Cummings does a good job of working in the necessary background about Basque politics in a natural way that did not drag even though I was already familiar with it. Even the title works well; there are prisoners here, though often in dungeons of their own making. I didn't realise this was a sequel to Cummings's first novel, A Spy by Nature. The book works fine as a stand-alone. Sufficient information was provided for me to understand where Milius was coming from. I will certainly go back now and find that novel and others by Cummings.