There’s the horror-movie version: a shadow with a knife, the one who escaped from the hospital on the hill during that storm. It’s the person living in the walls.

In mystery novels, it might be the smiling stranger, the one with the passing knowledge of poisons. It’s the relative left out of the will, or the one recently added to it. It’s the jealous colleague at the museum who wants to be the first to announce the new archeological discovery. It’s the overly helpful person who follows the detective around.

On the all-murder, true-crime channel, it’s the new neighbor with the boat, the one in his midforties to midfifties with the tan who has no past and who recently purchased a human-sized cooler. It’s the person who lives in the shack in the woods. It’s the unseen figure on the corner of the street.

On all crime shows, it’s usually the third person the cops interview. It’s the one you sort of think it is.

In life, the murderer is anyone. The reasons, the methods, the circumstances—the paths to becoming a murderer are as numerous as the stars. Understanding this is the first step to finding a murderer. You have to shut down the voices in your mind that say, “It has to be this person.” Murderers aren’t a type. They’re anyone.

Stevie put her head against the cool of the window and watched the moose sign go by.

“No moose,” she whispered.

Element Walker. Stevie could see her now, almost physically. Artist. Try-too-hard. Friendly. The girl with the bruises on her shins from climbing, with the holes in the toes of her cheap satin slipper shoes. The girl with the baby socks tied in her hair and the old cheerleader skirt. Ellie, who had a saxophone as a best friend even though she couldn’t play. The girl with the bottle of warm champagne she brought from France that she shared with two people she had just met.

Ellie, did you kill someone?

Did you mean to do it?

Stevie tried to propel her thoughts into the mountain air, as if texting Ellie with her mind. Tell me. I can help you. I’m sorry.

Why was she sorry? She had made the right conclusion. She hadn’t actually called security—Nate did that. All she did was ask a question.

The day had gone gray and the rock walls of the road menaced on either side. This was a hard, beautiful place. It had many nooks, but it was cold and high. Ellie was a creature of color, of people. Stevie saw her as she was on the first day of school, dressing as a messy punk cheerleader with her matted hair bound up in little socks. And then, later that day, dying her clothes pink in the bath as she drank champagne with Stevie and Janelle and held court. Ellie liked to perform, not hide out away from society.

No. The facts were the facts. She lined them up, measured them. Ellie had written the script and stolen the computer. That was all she said, and it was true. It was true. She could not be blamed for what was true.

A couple of days before Hayes’s death, someone took Janelle’s pass when they were at yoga in the art barn. It could have been anyone. The bag was just sitting out in the hall. But it was someone who knew Janelle had access to the maintenance shed. Someone went into the maintenance shed using Janelle’s pass and unloaded a massive amount of dry ice from the storage container. It weighed hundreds of pounds. It would have had to have been moved using a hand truck, or a golf cart, something large. From there, it was probably taken down the hatch entrance to the tunnel in the woods. Those blocks would have had to have been carried down the steps, down the tunnel, one by one. Then the room was closed up. To do what? Presumably create fog. But that’s not what dry ice does when you leave that much of it in a space for that long.

She could see Hayes or Ellie getting the science of it wrong. Neither one of them were big on science, as far as she knew. She could see Ellie messing around to create something for effect, but . . .

It never really made sense. Unless Hayes thought he could do some big fog scene or Ellie thought she would mess up his filming. . . .

But why make a big special effect when you don’t have anyone down there to film it? And there were easier ways to mess up his filming that would actually work.

If not Ellie, who?

She leaned her head against the cold of the window and the word thrummed in time with the moving coach: murder, murder, murder, murder . . .

Why did Hayes have to die? He was annoying. He cheated and used people. But in the end, he wasn’t worth killing.

But neither was Dottie, until she saw something she shouldn’t have.

Could Hayes have seen something? What was there even to see?

Her business was working on the Ellingham case, and the world had dropped the biggest, best opportunity right in her lap. Working with an author on a book about the case. This was her dream.

But Ellie was dancing in her peripheral vision.

They were turning onto the school grounds now, taking the treacherous path, the one with the trees so thick and low that they scraped the sides of the coach, and the steep slope that caused the gears to grind. There was the rushing river with the tiny wooden bridge. David had a point—getting through here was tough. It would be possible, she supposed, to go through the woods. But it would not be easy. And it would be terrifying in the dark. There was no way you could get through them without falling down the slope, tripping over the roots and fallen branches, falling into holes, knocking into rocks. And the only way over the river was the bridge. This was all as Albert Ellingham intended. The place was like a fortress. So if the bridge was watched and the back road was watched . . . how did Ellie magic her way out? Getting out of the locked room was almost nothing compared to this.

They were cresting now, passing between the dual sphinx statues. The coach stopped under the Great House portico and she stepped out into a slap of mountain breeze. Would it hurt just to have a look? Just a little look around, to satisfy whatever it was that was eating at her thoughts?

Stevie walked around the perimeter of the Great House. The back of the building was walled off, enclosing the sunken garden. She wasn’t sure which basement window Ellie was supposed to have escaped from, but there were only a few possibilities. The basement-leading windows had deep window wells, and these were covered over by grates. Stevie squatted down and pulled on one. It was firmly closed.

Forget where Ellie went—how did she even get out of the basement? Stevie couldn’t answer the first question until she answered the second. And there was someone who would know that answer. She found him in his usual place, at the big wooden desk right by the entrance door to the Great House.

“Just saying hi,” she said as she stepped into the massive vestibule.

Larry looked up from something he was writing on a clipboard.

“Hi,” he said. “Also, no.”

“I didn’t ask anything.”

“You didn’t have to. Whatever it is, no.”

She pulled over a folding chair that was by the door and sat across from him.

“I went to Burlington today,” she said.

“I’m glad to hear it.”

“To meet with Dr. Fenton, who wrote Truly Devious. Did you read that one?”

“I can’t remember,” he said, still reading down whatever it was on the clipboard.

There was a smell in the Great Hall that was unlike anything else at Ellingham. Ellingham was all outdoorsy and wood smoke. The Great Hall smelled of polish, of leather, of cigarettes last smoked in 1938 whose molecules had infested the wood and crystal and marble and produced some new, ancient smell. It smelled of wealth. Not money—wealth. It was not like the pong of Fenton’s cigarettes, which was stuck in Stevie’s hair and her hat. Her vinyl coat was impervious. All hail the vinyl.

“Okay,” she said when Larry refused to look up. “I was going to ask something.”

Larry clicked his pen in warning.

“I wanted to know if you would show me where Ellie got out.”

“I think I’ve answered that,” he said.

“Isn’t it better that I come to you and ask?”

“Yes. The answer is still no.”

“Oh, come on,” she said, lowering her voice and leaning down over the desk a bit. “Don’t I deserve to see?”

Larry’s face suggested that she did not.

“Come on,” Stevie tried again, this time with a hint of sadness. “I feel . . . responsible. I mean, I brought her here, and if a bear ate her . . .”

Nothing. Larry was like the mountain rock they stood upon. She tried to look distraught, but didn’t know how to make that happen. She ended up sticking out her lower lip a bit. Larry rolled his eyes and cast a look around the empty Great Hall.

“I’ll get you plain coffee K-Cups.”

“Go, Stevie,” he said.

“All I’m asking is to see where it happened. That’s all. It . . . freaks me out. I brought her here. Or, what I said did. I just want to see it.”

Larry clicked his pen a few more times.

“If I show you, will you stop?” he asked.

“Definitely,” she said.

Larry tipped his chair back a few inches, lowered his chin, and looked back into the half-open security office door next to him.