The second book in the Rob Ryan and Cassie Maddox series, 2008

Some nights, if I’m sleeping on my own, I still dream about Whitethorn House. In the dream it’s always spring, cool fine light with a late-afternoon haze. I climb the worn stone steps and knock on the door-that great brass knocker, going black with age and heavy enough to startle you every time-and an old woman with an apron and a deft, uncompromising face lets me in. Then she hangs the big rusted key back on her belt and walks away down the drive, under the falling cherry blossom, and I close the door behind her.

The house is always empty. The bedrooms are bare and bright, only my footsteps echoing off the floorboards, circling up through the sun and the dust motes to the high ceilings. Smell of wild hyacinths, drifting through the wide-open windows, and of beeswax polish. Chips of white paint flaking off the window sashes and a tendril of ivy swaying in over the sill. Wood doves, lazy somewhere outside.

In the sitting room the piano is open, wood glowing chestnut and almost too bright to look at in the bars of sun, the breeze stirring the yellowed sheet music like a finger. The table is laid ready for us, five settings-the bone-china plates and the long-stemmed wineglasses, fresh-cut honeysuckle trailing from a crystal bowl-but the silverware has gone dim with tarnish and the heavy damask napkins are frilled with dust. Daniel’s cigarette case lies by his place at the head of the table, open and empty except for a burnt-down match.

Somewhere in the house, faint as a fingernail-flick at the edge of my hearing, there are sounds: a scuffle, whispers. It almost stops my heart. The others aren’t gone, I got it all wrong somehow. They’re only hiding; they’re still here, for ever and ever.

I follow the tiny noises through the house room by room, stopping at every step to listen, but I’m never quick enough: they slide away like mirages, always just behind that door or up those stairs. The tip of a giggle, instantly muffled; a creak of wood. I leave wardrobe doors swinging open, I take the steps three at a time, I swing round the newel post at the top and catch a flash of movement in the corner of my eye: the spotted old mirror at the end of the corridor, my face reflected in it, laughing.

This is Lexie Madison’s story, not mine. I’d love to tell you one without getting into the other, but it doesn’t work that way. I used to think I sewed us together at the edges with my own hands, pulled the stitches tight and I could unpick them any time I wanted. Now I think it always ran deeper than that and farther, underground; out of sight and way beyond my control.

This much is mine, though: everything I did. Frank puts it all down to the others, mainly to Daniel, while as far as I can tell Sam thinks that, in some obscure and slightly bizarro way, it was Lexie’s fault. When I say it wasn’t like that, they give me careful sideways looks and change the subject-I get the feeling Frank thinks I have some creepy variant of Stockholm syndrome. That does happen to undercovers sometimes, but not this time. I’m not trying to protect anyone; there’s no one left to protect. Lexie and the others will never know they’re taking the blame and wouldn’t care if they did. But give me more credit than that. Someone else may have dealt the hand, but I picked it up off the table, I played every card, and I had my reasons.

This is the main thing you need to know about Alexandra Madison: she never existed. Frank Mackey and I invented her, a long time ago, on a bright summer afternoon in his dusty office on Harcourt Street. He wanted people to infiltrate a drug ring in University College Dublin. I wanted the job, maybe more than I had ever wanted anything in my life.

He was a legend: Frank Mackey, still in his thirties and already running undercover operations; the best Undercover agent Ireland’s ever had, people said, reckless and fearless, a tightrope artist with no net, ever. He walked into IRA cells and criminal gangs like he was walking into his local pub. Everyone had told me the story: when the Snake-a career gangster and five-star wacko, who once left one of his own men quadriplegic for not buying his round-got suspicious and threatened to use a nail gun on Frank’s hands, Frank looked him in the eye without breaking a sweat and bluffed him down till the Snake slapped him on the back and gave him a fake Rolex by way of apology. Frank still wears it.

I was a shiny green rookie, only a year out of Templemore Training College. A couple of days earlier, when Frank had sent out the call for cops who had a college education and could pass for early twenties, I had been wearing a neon yellow vest that was too big for me and patrolling a small town in Sligo where most of the locals looked disturbingly alike. I should have been nervous of him, but I wasn’t, not at all. I wanted the assignment too badly to have room for anything else.

His office door was open and he was sitting on the edge of his desk, wearing jeans and a faded blue T-shirt, flipping through my file. The office was small and had a disheveled look, like he used it mainly for storage. The desk was empty, not even a family photo; on the shelves, paperwork was mixed in with blues CDs, tabloids, a poker set and a woman’s pink cardigan with the tags still on. I decided I liked this guy.

“Cassandra Maddox,” he said, glancing up.

“Yes, sir,” I said. He was average height, stocky but fit, with good shoulders and close-cut brown hair. I’d been expecting someone so nondescript he was practically invisible, maybe the Cancer Man from The X Files, but this guy had rough, blunt features and wide blue eyes, and the kind of presence that leaves heat streaks on the air where he’s been. He wasn’t my type, but I was pretty sure he got a lot of female attention.

“Frank. ‘Sir’ is for desk jockeys.” His accent was old inner-city Dublin, subtle but deliberate, like a challenge. He slid off the desk and held out his hand.

“Cassie,” I said, shaking it.

He pointed at a chair and went back to his perch on the desk. “Says here,” he said, tapping my file, “you’re good under pressure.”

It took me a second to figure out what he was talking about. Back when I was a trainee posted to a scuzzy part of Cork city, I had talked down a panicked teenage schizophrenic who was threatening to cut his own throat with his grandfather’s straight razor. I had almost forgotten about that. It hadn’t occurred to me, till then, that this was probably why I was up for this job.

“I hope so,” I said.

“You’re, what-twenty-seven?”

“Twenty-six.”

The light through the window was on my face and he gave me a long, considering look. “You can do twenty-one, no problem. Says here you’ve three years of college. Where?”

“Trinity. Psychology.”

His eyebrows shot up, mock-impressed. “Ah, a professional. Why didn’t you finish?”

“I developed an unknown-to-science allergy to Anglo-Irish accents,” I told him.

He liked that. “UCD going to bring you out in a rash?”

“I’ll take my antihistamines.”

Frank hopped off his desk and went to the window, motioning me to follow. “OK,” he said. “See that couple down there?”

A guy and a girl, walking up the street, talking. She found keys and let them into a depressing apartment block. “Tell me about them,” Frank said. He leaned back against the window and hooked his thumbs in his belt, watching me.