“I’ve drawn a to-scale map of the Strip, plotting out the locations of the first four murders.” Sloane tapped on each red X as she rattled off the locations. “The rooftop pool at the Apex, the stage in the main theater at the Wonderland, the exact location where Eugene Lockhart was sitting when he was shot, and…” Sloane came to stand before the last X. “The east-most bathroom on the casino floor of the Majesty.” She stared at us in anticipation. “The pattern isn’t where the UNSUB struck as in which casino. It’s the precise coordinates of the murder!”

An intense look settled over Dean’s features. “Coordinates as in latitude and longitude?”

I could feel him starting to sink into the killer’s perspective, integrating that information, when Sloane interjected.

“Not latitude. Not longitude.”

She uncapped her pen and drew a straight line connecting the first two victims. Then she did the same, connecting the second victim to the third victim and the third to the fourth. Finally, she added five more marks, closely clustered inside the boundaries of the Majesty. She connected them to the rest, one after the other, then turned back to us, her eyes alight.

“Now do you see?”

I did.

“It’s a spiral,” Dean said.

At his words, Sloane went back over it and sketched an arc over each of the straight lines. The resulting pattern looked like a seashell.

“Not just a spiral,” Sloane said, stepping back. “A Fibonacci spiral!”

Lia flopped down on the sofa and stared up at Sloane’s diagram. “I’m going to go out on a limb and guess that has something to do with the Fibonacci sequence.”

Sloane nodded emphatically. All energy, she looked at the window and, seeing no place left to write, bounded over to the adjacent wall.

“Let’s try some paper this time,” Judd interjected mildly.

Sloane stared at him very hard.

“Paper,” she said, as if it were a word in another language. “Right.”

Judd handed her a piece. She plopped unceremoniously down on the floor and began to draw. “The first non-zero number in Fibonacci’s sequence is one. So you draw a square,” she said, doing just that, “where each side is one unit long.”

Beneath that square, she drew a second, identical square. “The next number in the sequence is also one. So now you have one and one….”

“And one plus one is?” She didn’t wait for an answer. “Two.” Another square, this one twice as big as each of the first.

“Two plus one is three. Three plus two is five. Five plus three is eight….” Sloane kept drawing squares, moving counterclockwise as she drew, until she ran out of space.

“Now imagine I kept going,” she said, shooting Judd a very pointed look that I interpreted to mean that she thought he’d erred in forbidding her to draw on the wall. “And imagine I did this.…” She started drawing arcs through the diagonal of each square.

“If I kept going,” she said, “and added two more squares, it would look exactly”—she turned to the spiral on the window—“like that.”

I looked from Sloane’s drawing to the layout of Vegas she’d drawn onto the window. She was right. Starting with the Apex, the killer was spiraling in. And if Sloane’s calculations were correct—and I had no reason to doubt that they were—our UNSUB was doing so in a precise and predictable fashion.

Sloane began scrawling the numbers of the Fibonacci sequence across the margins of the page, and I remembered that the first time she’d told us about the sequence, she’d said that it was everywhere. She’d said that it was beautiful.

She’d said that it was perfection.

You see that same thing when you look at this pattern. I addressed the UNSUB. Its beauty. Its perfection. Inked into Alexandra Ruiz’s wrist. Burned into the magician’s. Written on the old man’s skin. Carved into Camille’s flesh.

You’re not just sending a message. You’re creating something. Something beautiful.

Something holy.

“Where’s the next location?” Dean asked. “The next kill-point on the spiral—where is it?”

Sloane turned back to the window and tapped her finger just below the fifth X she’d drawn. “It’s here,” she said. “At the Majesty. All of the remaining kill-points are. The closer you get to the heart of the spiral, the closer they get to each other.”

“Where at the Majesty?” Dean asked Sloane.

If the UNSUB continued killing a person a day, we might be minutes away from the next murder—and no more than hours.

“The Grand Ballroom,” Sloane murmured, staring at the pattern inked onto the window, lost in what she saw. “That’s where it has to be.”

YOU

The knife is next.

Water. Fire. Impaling the old man on an arrow. Strangling Camille. Then comes the knife. That’s the way this is done. That is how it must be.

You sit on the floor, your back to the wall, the blade carefully balanced on one knee.

Water.

Fire.

Impaling.

Strangling.

One, two, three, four…

Knife will make five. You breathe in the weapon’s numbers: the exact weight of the blade, the speed with which you will slice it across your next target’s throat.

You breathe out.

Water. Fire. Impaling. Strangling. The knife is next. And then—and then—