Dean shot a sideways glance at Agent Sterling. “Just how disorganized was Trina Simms’s murder?”

I saw the logic to Dean’s question immediately: Clark fit the profile for a disorganized killer almost exactly.

“He followed the MO,” Agent Sterling said. “He just didn’t do it well.”

That’s why you killed him, I thought, addressing the words to our remaining UNSUB. You were both playing at the same game, but he messed up. He was going to get himself caught. Maybe he was going to get you caught, too.

“Did they know each other?” I asked. “Clark and our UNSUB—I’m betting they knew about each other, but had they actually met?”

“He’d want to keep them as separate as possible.” Dean didn’t specify who he was. Under the circumstances, he didn’t have to. “The less interaction they have with each other, the more control he has over the situation. This is his game, not theirs.”

It wasn’t enough to profile Clark or our UNSUB. At the end of the day, this all came back to Redding. I pictured him sitting across the table from me. I heard myself asking the questions, heard his replies. I walked through them, step by step, thinking all the while that I was missing something.

You sent Clark after Trina, I thought. Who did you send after Emerson?

The nagging feeling that there was something I wasn’t seeing intensified. I sat very still, and then suddenly, all the inconsequential details melted away until there was only one thing left. One detail.

One question.

“Lia,” I said urgently, “you’re sure that Redding didn’t lie in response to any of my questions?”

She inclined her head slightly—clearly, she didn’t think the question merited a verbal response.

“I asked him how he chose the victims.” I looked around the room to see if anyone’s mind would take the same path mine had. “I said, how do you choose who dies, and do you remember what he said?”

“He said I don’t.” Dean was the one who answered. I doubted he’d forgotten a single word his father had uttered in that meeting—in any of their meetings.

“If he doesn’t choose the victims,” I said, looking from Dean to Sterling to Briggs, “who does?”

There was a beat of silence.

“They do.”

I hadn’t expected the answer to come from Michael, but maybe I should have. He and Lia had met Clark, and he was the one who’d recognized the anger in the other boy.

She wasn’t like that, Clark had said when it had come out that Emerson had been sleeping with their professor—but he hadn’t believed the words he was saying. And that meant that he had believed that Emerson was like that. That she was less and worthy of scorn. That she deserved to be degraded.

He’d had pictures of her hidden under his bed.

Clark had been obsessed with Emerson. He’d loved her, and he’d hated her, and she’d turned up dead. The only reason he hadn’t been a viable suspect in her murder was that he had an alibi.

“Redding had the UNSUBs choose victims for each other.” Michael was still talking—and his thoughts were in sync with mine. “Clark chose Emerson, but someone else killed her. It’s Strangers on a Train.”

“Alfred Hitchcock,” Sloane chimed in. “1951 film. One hour and forty-one minutes long. The movie postulates that the most foolproof way to get away with murder is for two strangers to take out each other’s targets.”

“That way,” Briggs said softly, “each killer has an alibi when their target dies.”

Like Clark had been in a room with hundreds of others taking a test when Emerson had been killed.

The dominoes fell, one by one in my head.

Like Christopher Simms was in a meeting with Briggs when someone killed his mother.

I sat on the stairs, waiting. The FBI had been attempting to locate Christopher Simms for the past fourteen hours. Daniel Redding had promised us another body today, and all I could do was wait—to see if we were right, to see if they caught him in time. I couldn’t go up the stairs. I couldn’t go down them. I couldn’t do anything but sit there, halfway in between, obsessing over the evidence and praying that when the phone rang, it would be to tell us they had apprehended the suspect, not to inform us that we had a fifth victim.

No matter how many times I went over the case, the details stayed the same. Clark had chosen Emerson, and someone else had killed her at a time when Clark’s alibi was ironclad. That person had then chosen a victim—Trina Simms.

I could still see the look in Christopher’s eyes when he’d grabbed my arm and wrenched me off the couch. He was sick of being under his mother’s thumb. What better payback than to see her killed—in a roundabout way—by the man she fancied herself in love with?

It all came back to Daniel Redding. Christopher may have chosen Trina to die, but Redding had been the one to choose Christopher as an apprentice. Dean’s father had probably used Trina to get to her son. He’d almost certainly told Clark to hold off on killing Trina until she’d received a visit from Dean.

How long has he been planning this? How many moving parts did he set in motion before Emerson’s body was found on that lawn? I turned to my left and glanced at the wall. The stairway was lined with portraits—serial killers decorating our walls like they were family.

The irony did not escape me.

In my hand, I held the Rose Red lipstick. I took the cap off and turned the bottom of the tube until the dark red color peeked over the edge of the plastic casing.

You will never find the man who murdered your mother. Redding’s words were there in the back of my mind, mocking me.

“Mind if I keep you company while we wait?”

I glanced back over my shoulder at Dean, who was standing near the top of the stairs.

“Grab a seat,” I told him. Instead of sitting on one of the steps above me, he walked until he reached my step and lowered himself down next to me. The staircase was wide enough that there was still space between us, but narrow enough that there wasn’t much. His eyes fell on the tube of lipstick in my hands.

He knows, I thought. He knows this was Locke’s, and he knows why I kept it.

“I can’t stop thinking about them,” Dean said after a moment. “Gary Clarkson. Christopher Simms. They were never my father’s endgame.”

I lowered the lipstick back into the tube and capped it. “You were,” I said, knowing it was true, knowing that somehow, this had always been about Dean.

Dean closed his eyes. I could feel him next to me, feel each breath in and each breath out. “I can’t decide if my father engineered this whole thing just so I’d be forced to go see him, or if he was banking on one of his students eventually trying to prove himself the better man by killing me.”

Dean’s eyelids lifted, and I thought through his words. Emerson’s murderer had killed Clark. That was the work of an UNSUB who wanted to be Redding’s only apprentice. His only heir. His only son.

“Your father doesn’t want you dead,” I told Dean. For Redding, that would be a last resort. He’d kill Dean only if he believed he’d truly lost him—and Daniel Redding was incapable of ever believing he’d truly lost.

“No,” Dean agreed, “he doesn’t want me dead, but if one of the UNSUBs had escalated, if one of them had come here to kill me, I would have defended myself.”

Maybe, in Redding’s mind, that was the way this was supposed to end, with Dean killing the others. Redding saw Dean as an extension of himself. Of course he thought Dean would win—and if Dean didn’t, well, then maybe Daniel Redding believed that he deserved to die. For being weak.

For not being his father’s son.

The phone rang. My muscles tensed. I was frozen, unable to move, unable to breathe. Two seconds later, the phone stopped ringing. Someone had answered.

Please let them have found him in time. Please let them have found him in time.

“Dean.” I managed to force his name out of my suddenly dry mouth. He sat, just as immobile, beside me. “Last summer, after everything that happened, Michael told me to figure out how I felt. About you.”