I tried to parse what Sloane was saying. If you generated a total of twenty-seven dates based on the Fibonacci sequence, you ended up with a pattern that was consistent not only with our killer’s pattern, but also with a series of nine murders committed over a decade ago.

I need nine.

“The case from eleven years ago,” I said, commanding Sloane’s attention. “Did they ever catch the killer?”

Sloane tilted her head to the side. “I’m not sure. I was just looking at the dates. Give me a second.” Sloane’s eidetic memory meant that she automatically memorized anything she read. After going back over the files in her head, she answered the question. “The case is still open. The killer was never caught.”

Most serial killers don’t just stop, I thought, Agent Sterling’s words echoing in my mind. Not unless someone stops them.

“Sloane,” I said, trying to keep my mind from racing too fast. “The killer who ended his run on January first—how did he kill his victims?”

This time, it took Sloane a fraction of a second to pull the information to the front of her mind. “He slit their throats,” she said. “With a knife.”

I tried Sterling’s cell, then Briggs’s. Neither of them answered. They were probably up all night, I thought, talking to witnesses, trying to figure out who, if anyone, hypnotized Aaron’s “friend” to deliver that message.

“I’m going to talk to Dean,” I told Sloane. “Catch him up on what you just told me.” I took in the dark circles under Sloane’s eyes. “You should try getting some sleep.”

Sloane frowned. “Giraffes only sleep four and a half hours a day.”

Knowing a losing battle when I saw one, I let her be. Making my way quietly across the suite, I stopped outside Dean’s room. The door was cracked open. I placed my hand flat on the wood.

“Dean?” I called. When he didn’t respond, I knocked lightly. The door drifted inward, and I caught sight of Dean sleeping. He’d pushed his bed to one side of the room and slept with his back to the wall. His blond hair fell gently into his eyes. His face was free of tension.

He looked peaceful.

I began backing out of the doorway. The floor creaked, and Dean bolted up in bed, his eyes unseeing, his hand thrust out in front of him. His fingers were curved, like he’d caught a ghost by the neck.

“It’s me,” I said quickly. When he still didn’t register my presence, I turned on the light. “It’s me, Dean.” I stepped toward the bed. It’s just me.

Dean’s head swiveled. He stared through me. And then a moment later, he was back. His eyes focused on mine. “Cassie.” He said my name the way another person might rattle off a prayer.

“Sorry,” I told him, coming closer. “For waking you up.”

“Don’t be sorry,” Dean said, his voice rough.

I crawled onto the bed beside him. His hands found their way to the ends of my hair, his touch soft. He closed his eyes for a moment, taking in the warmth of my body. When he opened them, they were calmer, clear.

“Something’s wrong,” Dean said, observant as always. I wondered if he could see the tension in my shoulders. I wondered if he could feel it with his featherlight touch.

“Sloane found something.” I let his touch steady me, even as it steadied him. “She derived a series of twenty-seven dates from the Fibonacci sequence. Then she did a search on the FBI’s database for serial murders where one or more of the killings happened on New Year’s Day.”

“Briggs and Sterling gave her that kind of access?”

My facial expression must have answered that question for me.

“She hacked the FBI.” Dean paused. “Of course she did. She’s Sloane.”

“She found a decade-old case that fits the same pattern,” I told him. “Nine victims, killed on Fibonacci dates.”

“MO?” Dean asked.

“Killer used a knife. He attacked from behind and slit his victims’ throats. The first victim was a prostitute. I don’t have information on any of the others.”

“Nine bodies,” Dean repeated. “On dates derived from the Fibonacci sequence.”

I shifted my body, leaning into his. “Last night, the message was ‘I need nine.’ Need, Dean, not ‘want,’ not ‘I’m going to kill nine.’ Need.”

The number of victims mattered, the same way the numbers on the wrists did, the same way the dates did.

“The case Sloane found is still open,” I told Dean. “It was never closed. Sterling said that serial killers don’t just stop killing.”

Dean heard the question I hadn’t yet put into words. Could we be dealing with the same killer?

“Eleven years is a long time for a killer to deny himself,” Dean said. I saw the shift in Dean before his words confirmed it. “Each time I kill, I need more. To go without, for so long…”

“Is it even possible?” I asked Dean “Can an UNSUB kill nine people and then just…wait?”

“Our UNSUB just killed four people in four days,” Dean replied. “And now he’s waiting. Smaller scale, same concept.”

The numbers matter. The numbers told the UNSUB where to kill, when to kill, how long to wait. But making sure a portion of the sequence appeared on each victim’s wrist?

From the beginning, we’d read that as a message. What if the message was I’ve done this before?