LUCKY FOR me, the lovebirds paused in Símon’s doorway for a long, loud kiss. It gave me just enough time to duck out onto the balcony.

If Símon had lived on the second floor, I might have jumped. At most I’d have sprained an ankle or tweaked a knee. Nothing a frozen steak couldn’t fix. But that third flight would land me in the hospital. There’d be a report. Heidi would hear about it. She’d figure out soon enough that Símon and Serena were siblings, and then she’d come hard after my badge. I couldn’t risk that. My only option was to hunker down and wait it out.

I watched Símon and his date through a small gap in the curtains covering the French doors. They’d decided to take their nightcap at home. Símon, it seemed, wanted to showcase his stainless steel martini mixer. Either he was a little drunk already or he didn’t spend much time in his kitchen. It took a lot of opening and closing of cabinets before he had the gin and the vermouth and the olives lined up on the counter.

Meanwhile, my mind was running scenarios, none of them very pleasant.

My biggest fear was that Símon and his lady friend would choose to sip their cocktails under the stars. In that case, the best I could do would be to hide my face and shoulder my way past them. Símon had pounds on me, but I had sobriety and surprise on my side. I slipped out of my blazer, prepared to hold it like a cape in front of my head.

But the evening didn’t take that particular turn. These were working people with early start times. They could only fit so much into an evening. Once Símon found a pair of tiny plastic swords for the olives, they carried their martinis straight to the bedroom. I quit holding my breath, let out what felt like enough air for four people. Then I waited some more just in case Símon came back in search of snacks.

That was when I saw it, lying there on the small wrought iron table. A bright blue workbook called English on Your Lunch Break. I remembered when Sarah bought it. She took the title literally, had visions of tutoring Serena over grilled-tomato sandwiches and sun-brewed iced tea. The two of them were close—almost like sisters. Together, they made life under Anthony’s thumb bearable.

Seeing the book here now, my pulse turned electric. I scanned the rest of the balcony, spotted a small, tan duffel bag hidden behind a potted ficus tree. I walked over, opened it, found a stash of women’s clothes and toiletries. Things were looking up. So much so that I almost forgot I was on the verge of getting busted for B and E.

Priorities, I told myself. Time to get the hell out of here.

I opened the French doors just wide enough to slip through, then walked heel to toe across the living room. There was a jazz record playing somewhere in the recesses of the apartment. Símon was pulling out all the stops. Part of me felt jealous: Sarah and I hadn’t been on anything like a date in as long as I could remember, and lately our bedroom was strictly for sleep.

Back at the Jeep, I pulled out a flask from under the spare tire and did some drinking of my own. Then I spent an hour circling the block until a spot opened up directly across from Símon’s building. Serena had been there. She’d been staying there. Date night or not, there was a chance she might come back. The fact that she’d hidden her belongings behind a tree on the balcony only confirmed she was on the run. Whether she’d done something or was afraid of being blamed for something remained to be seen.

Unlike most cops, I love a good stakeout. There’s an adrenaline rush that comes with putting yourself in a position to see what nobody wants you to see. The adrenaline helps me think. And I had a hell of a lot to think about, starting with how I’d play it when Serena made her appearance. I couldn’t, despite direct orders, turn her over to Vincent. I’d be disposing of the person most likely to swear up and down that Sarah was no killer.

The more I thought about it, the more I became convinced I could pin it on the brother—whether he’d done it or not. All I needed was a little time to build the case. Meanwhile, I had to get word to Heidi’s three main suspects. Apart from the fact that they ran, Heidi had nothing on them. Nothing concrete. All they had to do was point the finger at each other, keep my ex-partner turning in circles. I’d tell them exactly what to say. Have Sarah implicate Serena, Anna implicate Sarah, Serena implicate Anna. Or maybe have each of them implicate the other two. Heidi would be blinded with reasonable doubt. Sarah would remain free.

A plan was starting to take shape. I worked it out one piece at a time. The siblings were my ticket back to a humdrum life. First, find Serena and put in a call to the tip line; second, hand Símon over to Vincent with a note that read “He killed your nephew.” It would be awfully damn convenient to have Símon disappear while Serena was in the box with Heidi. He’d look like a man who knew his sister was about to flip. And when Heidi’s team searched Símon’s condo, they’d find a few of Anthony’s prized possessions sitting on the top shelf of his bedroom closet.

Little by little, the lights went out in the buildings around me. I found myself kicking around the same question into the wee hours: did the fact that Serena was staying with Símon make it more or less likely that he killed Anthony? I mean actually killed Anthony. And if not him, then who? It wasn’t one of Vincent’s men. The killing was too personal, too sloppy. A pro wouldn’t stab him twenty-seven times, then leave the body behind. Who else had the motive and strength? Maybe Serena found herself a boyfriend. Maybe Anna had taken a lover. Maybe Sarah had, for that matter: I’d have been too checked out to notice.

But why dwell on maybes when there was a flesh-and-blood brother tailor-made for the part? The truth didn’t matter at all next to what I could prove. And if I could just find Serena, I was pretty sure I could prove that my wife hadn’t killed Anthony Costello.