I had felt this one coming for days. I flipped through the photos like flash cards and tried to concentrate on running the names in my head: Cillian Wall, Chloe Nelligan, Martina Lawlor… “Hit me,” I said.

Frank put the mugs down and started playing with my saltcellar, turning it carefully between his fingers. “I hate to bring this up,” he said, “but what can you do, sometimes life sucks. You’re aware that you’ve been-how shall I put this-a little jumpy lately, yeah?”

“Yeah,” I said, keeping my eyes on the photos. Isabella Smythe, Brian Ryan-someone’s parents either hadn’t been thinking too clearly, or had a weird sense of humor-Mark O’Leary… “I’m aware.”

“I don’t know if it’s because of this case or if it was going on already or what, and I don’t need to know. If it’s just stage fright, it might well vanish as soon as you’re inside that door. But here’s what I wanted to say to you: if it doesn’t, don’t panic. Don’t start second-guessing yourself, or you’ll talk yourself into losing your nerve, and don’t try to hide it. Use it. There’s no reason why Lexie shouldn’t be a little shaky right now, and there’s no reason why you shouldn’t make that work for you. Use what you’ve got, even if it’s not necessarily what you’d have chosen. Everything’s a weapon, Cass. Everything.”

“I’ll keep that in mind,” I said. The thought of Operation Vestal actually coming in useful did something complicated inside my chest, made it hard to breathe. I knew if I blinked Frank would notice.

“Think you can do that?”

Lexie, I thought, Lexie wouldn’t tell him to mind his own business and let her mind hers, which was my main instinct here, and she sure as hell wouldn’t answer. Lexie would yawn in his face, or tell him to quit nagging and lecturing like someone’s granny, or demand ice cream. “We’re out of biscuits,” I said, stretching-the photos slid off my stomach, all over the floor. “Go get some. Lemon creams,” and then I laughed out loud at the look on Frank’s face.

Frank graciously gave me Saturday night off-heart of gold, our Frankie-so Sam and I could say our good-byes. Sam made chicken tikka for dinner; for dessert I tried an incongruous tiramisu, which turned out looking ridiculous but tasting OK. We talked about small stuff, unimportant stuff, touching hands across the table and swapping the little things that new couples pass back and forth and save like beach finds: stories from when we were kids, the dumbest things we’d done as teenagers. Lexie’s clothes, hanging on the wardrobe door, shimmered in the corner like hard sun on sand, but we didn’t mention them, not once.

After dinner we curled up on the sofa. I had lit a fire, Sam had put music on the CD player; it could have been any evening, it could have been all ours, except for those clothes and for the fast ready beat of my pulse, waiting.

“How’re you doing?” Sam asked.

I had been starting to hope we could make it through the night without talking about tomorrow, but realistically this was probably too much to ask. “OK,” I said.

“Are you nervous?”

I thought this over. This situation was totally bananas on about a dozen different levels. I probably should have been petrified. “No,” I said. “Excited.”

I felt Sam nod, against the top of my head. He was running one hand over my hair in a slow, soothing rhythm, but his chest felt rigid as a board against mine, like he was holding his breath.

“You hate this idea, don’t you?” I said.

“Yeah,” Sam said quietly. “I do.”

“Why didn’t you stop it? It’s your investigation. You could have put your foot down, any time you felt like it.”

Sam’s hand stopped still. “Do you want me to?”

“No,” I said. That, at least, I knew for sure. “No way.”

“It wouldn’t be easy, at this stage. Now that the undercover operation’s up and running, it’s Mackey’s baby; I’ve no authority there. But if you’ve changed your mind, I’ll find a way to-”

“I haven’t, Sam. Seriously. I just wondered why you gave the OK to start with.”

He shrugged. “Mackey has a point, sure: we’ve nothing else on the case. This could be the only way to solve it.”

Sam has unsolveds with his name on them, every detective has, and I was pretty sure he could survive another one, as long as he was sure the guy hadn’t been after me. “You didn’t have anything last Saturday, either,” I said, “and you were dead against it then.”

His hand started moving again, absently. “That first day,” he said, after a while. “When you came down to the scene. You were messing with Mackey, do you remember? He was slagging you about your clothes and you were slagging back, almost like the way you used to with… when you were on Murder.”

He meant with Rob. Rob was probably the closest friend I’ve ever had, but then we had this huge complicated vicious fight and that was the end of that. I twisted round and propped myself on Sam’s chest so I could see him, but he was looking up at the ceiling. “I hadn’t seen you like that in a while,” he said. “That much bounce to you.”

“I’ve probably been pretty crap company, these last few months,” I said.

He smiled, just a little. “I’m not complaining.”

I tried to remember ever hearing Sam complain about anything. “No,” I said. “I know.”

“Then Saturday,” he said. “I know we were fighting and all”-he gave me a quick squeeze, dropped a kiss on my forehead-“but still. I realized afterwards: that was because we were both really into it, this case. Because you cared. It felt…” He shook his head, looking for the words. “DV’s not the same,” he said, “is it?”

I had mostly kept my mouth shut about DV. It hadn’t occurred to me, till then, that all that silence could have been plenty revealing, in its own way. “It needs doing,” I said. “Nothing’s the same as Murder, but DV’s fine.”

Sam nodded, and for a second his arms tightened around me. “And that meeting,” he said. “Right up until then, I’d been wondering should I pull rank and tell Mackey to bugger off for himself. This started off as a murder case, I’m down as lead detective, if I said no… But the way you were talking, all interested, thinking it out… I just thought, why would I wreck that?”

I had not seen this coming. Sam has one of those faces that fool you even when you know better: a countryman’s face, all ruddy cheeks and clear gray eyes and crow’s-feet starting, so simple and open that there couldn’t possibly be anything hidden behind it. “Thanks, Sam,” I said. “Thank you.”

I felt his chest lift and fall as he sighed. “It might turn out to be a good thing, this case. You never know.”

“But you still wish this girl had picked just about anywhere else to get herself killed,” I said.

Sam thought about that for a minute, twisting a finger delicately through one of my curls. “Yeah,” he said, “I do, of course. But there’s no point in wishing. Once you’re stuck with something, all you can do is make the best of it.”

He looked down at me. He was still smiling, but there was something else, something almost sad, around his eyes. “You’ve looked happy, this week,” he said simply. “It’s nice to see you looking happy again.”

I wondered how the hell this man put up with me. “Plus you knew I would kick your arse if you started making decisions for me,” I said.

Sam grinned and flicked the end of my nose with his finger. “That too,” he said, “my little vixen,” but there was still that shadow behind his eyes.

Sunday moved fast, after those long ten days, fast as a tidal wave built to bursting point and finally crashing down. Frank was coming over at three, to wire me up and get me to Whitethorn House by half past four. All the time Sam and I were going through our Sunday-morning routine-the newspapers and leisurely cups of tea in bed, the shower, the toast and eggs and bacon-that was hanging over our heads, a huge alarm clock ticking, waiting for its moment to explode into life. Somewhere out there, the housemates were getting ready to welcome Lexie home.