Agent Sterling held up a hand to stave off questions. “Let’s back up.” She glanced over at Briggs. “Start from the beginning.”

Briggs gave a curt nod, then flipped a switch. A flat screen near the front of the plane turned on. Briggs hit a button, and a crime scene photo appeared. In it, a woman with long, dark hair lay on the pavement. Her lips had a bluish tint. Her eyes were glassy. A sopping wet dress clung to her body.

“Alexandra Ruiz,” Agent Sterling narrated. “Twenty-two years old, college student majoring in pre-occupational therapy at the University of Arizona. She was found about twenty minutes after midnight on New Year’s Eve, floating facedown in the rooftop pool at the Apex Casino.”

“The Apex Casino.” Sloane blinked several times. “Las Vegas, Nevada.”

I waited for Sloane to tell us the square footage of the Apex, or the year it was founded. Nothing.

“Pricey.” Lia filled the void. “Assuming our victim was staying at the Apex.”

“She wasn’t.” Briggs brought up another photo, inset to one side of Alexandra’s, this one of a man in his early forties. He had dark hair with just a dusting of silver. The photo was a candid one. The man wasn’t looking at the camera, but I got the distinct feeling that he knew it was there.

“Thomas Wesley,” Briggs told us. “Former internet mogul, current world poker champion. He’s in town for an upcoming poker tournament and rented the penthouse suite at the Apex, with exclusive access to the rooftop pool.”

“I’m guessing our boy Wesley likes to party?” Lia asked. “Especially on New Year’s Eve?”

I stopped examining Thomas Wesley’s picture as my eyes were drawn upward toward Alexandra’s. You and some friends thought it would be a blast to spend New Year’s Eve in Vegas. You got invited to a party. Maybe even the party. Her dress was turquoise. Her shoes were black, high-heeled. One heel had been snapped off. How did you break your heel?

Were you running? Did you struggle?

“Did she have any bruises?” I asked. “Any sign that she’d been held under the water?”

Any sign that she fought back?

Agent Sterling shook her head. “There were no signs of a struggle. Her blood alcohol level was high enough that police assumed it was an accident. Tragic, but not criminal.”

That would explain why the police hadn’t connected their first two victims. They hadn’t even realized Alexandra was a victim.

“How do we know it wasn’t an accident?” Lia swung her legs over the side of her seat, letting them dangle off.

“The calling card.” Dean and I answered at the exact same time.

I turned my mind from Alexandra to the UNSUB. You made it look like an accident, but left something to tell the police that it wasn’t. If they were smart enough, if they connected the pieces of the puzzle, they’d see. See what you were doing. See the elegance in it.

See how clever you are.

“What was it?” I voiced the question Dean had asked earlier. “What did the UNSUB leave?”

Another click from Briggs, another picture on the screen, this one a close-up of a wrist. Alexandra’s. Her arm lay palm-up on the pavement. I could see the veins beneath her skin, and just above them, on the outside edge of her wrist, were four numbers, inked into her skin in fancy script: 3213. The ink was dark brown, with a slight orange tint to it.

“Henna,” Sloane offered, playing with the edge of her sleeve, judiciously avoiding eye contact with the rest of us. “A dye derived from the flowering plant Lawsonia inermis. Henna tattoos are temporary and, at any given time, less common than permanent tattoos by a factor of about twenty to one.”

I could feel Dean beside me, processing this information. His gaze was locked onto the picture, as if he could will it to tell him the full story. “The tattoo on her wrist,” he said. “That’s the calling card?”

You’re not just leaving messages. You’re leaving them inked onto the bodies of your victims.

“Is there any way to get a time stamp on the tattoo?” I asked. “Did he mark her, then drown her, or drown her, then mark her?”

Briggs and Sterling exchanged a look. “Neither.” Sterling was the one who answered the question. “According to her friends, she got the tattoo herself.”

As we processed that information, Briggs cleared the screen and brought up a new photo. I tried to look away, but couldn’t. The corpse on the screen was covered in blisters and burns. I couldn’t tell if the victim was male or female. There was only one patch of unmarred skin.

The right wrist.

Briggs gave us a close-up.

“4-5-5-8.” Sloane read out loud. “3-2-1-3. 4-5-5-8.” She stopped talking, but her lips kept moving as she went over and over the numbers.

Meanwhile, Dean and I were staring at the photograph.

“Not henna this time,” he said. “This time I had the numbers burned into my target’s skin.”

My preferred pronoun for profiling was you. I talked to the killer, to the victims. But when Dean slipped into an UNSUB’s head, he imagined being the killer. Doing the killing.

Given who and what his father was—and the way Dean couldn’t shake the fear that he’d inherited some trace of monstrousness—that didn’t surprise me. Every time he profiled, he faced that fear head-on.

“I suppose you’re going to tell us victim number two burned the numbers into his own arm?” Lia asked Briggs. She did a good job of sounding unaffected by the gruesomeness of what we were seeing, but I knew better. Lia was an expert at masking her true reactions, showing only what she wanted the world to see.