When I made the Murder squad, I had already had my new work clothes-beautifully cut suits in materials so fine they felt alive to your fingers, shirts with the subtlest of blue or green pinstripes, rabbit-soft cashmere scarves-hanging in my wardrobe for almost a year. I love the unspoken dress code. It was one of the things that first fascinated me about the job-that and the private, functional, elliptical shorthand: latents, trace, Forensics. One of the Stephen King small towns where I was posted after Templemore had a murder: a routine domestic-violence incident that had escalated beyond even the perpetrator's expectations, but, because the man's previous girlfriend had died in suspicious circumstances, the Murder squad sent down a pair of detectives. All the week they were there, I had one eye on the coffee machine whenever I was at my desk, so I could get my coffee when the detectives got theirs, take my time adding milk and eavesdrop on the streamlined, brutal rhythms of their conversation: when the Bureau comes back on the tox, once the lab IDs the serrations. I started smoking again so I could follow them out to the car park and smoke a few feet from them, staring blindly at the sky and listening. They would give me brief unfocused smiles, sometimes a flick of a tarnished Zippo, before dismissing me with the slightest angle of a shoulder and going back to their subtle, multidimensional strategies. Pull in the ma first, then give him an hour or two to sit at home worrying about what she's saying, then get him back in. Set up a scene room but just walk him through it, don't give him time for a good look.

Contrary to what you might assume, I did not become a detective on some quixotic quest to solve my childhood mystery. I read the file once, that first day, late on my own in the squad room with my desk lamp the only pool of light (forgotten names setting echoes flicking like bats around my head as they testified in faded Biro that Jamie had kicked her mother because she didn't want to go to boarding school, that "dangerous-looking" teenage boys spent evenings hanging around at the edge of the wood, that Peter's mother once had a bruise on her cheekbone), and then never looked at it again. It was these arcana I craved, these near-invisible textures like a Braille legible only to the initiated. They were like thoroughbreds, those two Murder detectives passing through Ballygobackwards; like trapeze artists honed to a sizzling shine. They played for the highest stakes, and they were experts at their game.

I knew that what they did was cruel. Humans are feral and ruthless; this, this watching through cool intent eyes and delicately adjusting one factor or another till a man's fundamental instinct for self-preservation cracks, is savagery in its most pure, most polished and most highly evolved form.

We heard about Cassie days before she joined the squad, probably before she even got the offer. Our grapevine is ridiculously, old-ladyishly efficient. Murder is a high-pressure squad and a small one, only twenty permanent members, and under any added strain (anyone leaving, anyone new, too much work, too little work), it tends to develop a tinge of cabin-fevery hysteria, full of complicated alliances and frantic rumors. I am usually well out of the loop, but the Cassie Maddox buzz was loud enough that even I picked up on it.

For one thing she was a woman, which caused a certain amount of poorly sublimated outrage. We are all well trained to be horrified by the evils of prejudice, but there are deep stubborn veins of nostalgia for the 1950s (even among people my age; in much of Ireland the fifties didn't end until 1995, when we skipped straight to Thatcher's eighties), when you could scare a suspect into confession by threatening to tell his mammy and the only foreigners in the country were med students and work was the one place where you were safe from nagging females. Cassie was only the fourth woman Murder had taken on, and at least one of the others had been a huge mistake (a deliberate one, according to some people) who had entered squad lore when she nearly got herself and her partner killed by freaking out and throwing her gun at a cornered suspect's head.

Also, Cassie was only twenty-eight and only a few years out of Templemore. Murder is one of the elite squads, and nobody under thirty gets taken on unless his father is a politician. Generally you have to spend a couple of years as a floater, helping out wherever someone is needed for legwork, and then work your way up through at least one or two other squads. Cassie had less than a year in Drugs under her belt. The grapevine claimed, inevitably, that she was sleeping with someone important, or alternatively that she was someone's illegitimate daughter, or-with a touch more originality-that she had caught someone important buying drugs and this job was a payoff for keeping her mouth shut.

I had no problem with the idea of Cassie Maddox. I had been in Murder only a few months, but I disliked the New Neanderthal locker-room overtones, competing cars and competing aftershaves and subtly bigoted jokes justified as "ironic," which always made me want to go into a long pedantic lecture on the definition of irony. On the whole I prefer women to men. I also had complicated private insecurities to do with my own place on the squad. I was almost thirty-one and had two years as a floater and two in Domestic Violence, so my appointment was less sketchy than Cassie's, but I sometimes thought the brass assumed I was a good detective in the mindless preprogrammed way that some men will assume a tall, slim, blond woman is beautiful even if she has a face like a hyperthyroid turkey: because I have all the accessories. I have a perfect BBC accent, picked up at boarding school as protective camouflage, and all that colonization takes awhile to wear off: even though the Irish will cheer for absolutely any team playing against England, and I know a number of pubs where I couldn't order a drink without risking a glass to the back of the head, they still assume that anyone with a stiff upper lip is more intelligent, better educated and generally more likely to be right. On top of this I am tall, with a bony, rangy build that can look lean and elegant if my suit is cut just right, and fairly good-looking in an offbeat way. Central Casting would definitely think I was a good detective, probably the brilliant maverick loner who risks his neck fearlessly and always gets his man.

I have practically nothing in common with that guy, but I wasn't sure anyone else had noticed. Sometimes, after too much solitary vodka, I came up with vivid paranoid scenarios in which the superintendent found out I was actually a civil servant's son from Knocknaree and I got transferred to Intellectual Property Rights. With Cassie Maddox around, I figured, people were much less likely to spend time having suspicions about me.

When she finally arrived, she was actually sort of an anticlimax. The lavishness of the rumors had left me with a mental picture of someone on the same TV-drama scale, with legs up to here and shampoo-ad hair and possibly a catsuit. Our superintendent, O'Kelly, introduced her at Monday-morning parade, and she stood up and said something standard about being delighted to join the squad and hoping she'd live up to its high standards; she was barely medium height, with a cap of dark curls and a boyish, slim, square-shouldered build. She wasn't my type-I have always liked girlie girls, sweet, tiny bird-boned girls I can pick up and whirl around in a one-armed hug-but there was something about her: maybe the way she stood, weight on one hip, straight and easy as a gymnast; maybe just the mystery.

"I heard her family are Masons and they threatened to have the squad dissolved if we didn't take her on," said Sam O'Neill, behind me. Sam is a stocky, cheerful, unflappable guy from Galway. I hadn't had him down as one of the people who would get swept up in the rumor tsunami.