“Serious inquiries only, please,” said Hazel.

“Van Stavern’s package is from Inverness,” Emrys said, blotting the rainwater from his arms. “In Scotland!”

“Ah, it makes sense now,” Serena said, tapping her chin theatrically. “He’s the love child of Nessie and a leprechaun.”

Hazel rolled her eyes. “Leprechauns are Irish.”

“Leprechauns are make-believe!” Serena said. “And the ‘Sorcerer of #701’ is a sad old man with no family. Leave him be.”

Hazel looked back at Emrys and shrugged. It’s not as if they’d ever dream of bothering the man. It was fun, though, to have a little bit of mystery right there in their apartment building.

Emrys had never even seen Alyx Van Stavern, aside from a fleeting glimpse of a sour face peering down from the top-floor window on moving day—a face that was quickly replaced with drawn curtains. When he’d asked Hazel about the man who lived in the penthouse apartment, her eyes had grown wide.

She’d told him what little she knew of the strange recluse who’d moved in a year before and had rarely—if ever—left his apartment since. He hadn’t even answered the door when Hazel had trudged upstairs with her mother’s “welcome to the neighborhood” casserole, although she was certain he’d been home. She’d smelled an odd odor coming through his door, like old eggs. On another occasion weeks later, she’d heard a howl, like an animal in pain, coming from upstairs, but her mother claimed it was just an alley cat on the roof. Aside from that, the only sign that the man existed was the steady influx of packages bearing postmarks from all over the world—Budapest and Sighișoara and Château de Brissac—which the building’s super, Mr. Popov, carried upstairs and left on the seventh-floor landing. (Hazel had asked.)

Emrys found himself composing, expanding, and revising an imaginary wiki entry on their local “Sorcerer of #701” with each new piece of information he gleaned. Of course, he wouldn’t actually submit an entry that was 100 percent hearsay and speculation. He took the site too seriously for that. The mods were counting on him.

“My dads are at some party, but they left us a frozen pizza,” Serena said, and she took their damp towels and motioned for them to come inside. “My brother’s at his friend’s house. So the apartment is ours for the night. I’ve got a super gory movie picked out already. You’ll love it.”

“Your parents are out?” said Emrys. “In the storm? Aren’t you worried?”

Serena flicked her wrist as if batting the suggestion away. “This is New Rotterdam,” she said. “If I worried about rain, I’d be worried all the time. And what fun would that be?”

Emrys forced himself to chuckle, but hardly any sound came out. Worried all the time. No fun. Was that directed at him?

“Oh! You haven’t told me yet,” said Serena, as she sat sideways in a big reclining chair, draping her legs over the side. “How was your little adventure? Did you get photographic proof of the long-limbed dog?”

“It’s the Long-Necked Dog,” Hazel corrected. Less fiercely, she added, “And … no. Not this time.”

“We were too early,” put in Emrys.

“Yes.” Serena sniffed. “I’m sure that was the problem.”

Serena’s movie selection was as gruesome as she promised—a bloody affair in which a group of teenagers were eliminated one by one by a mysterious knife-wielding assassin. Serena laughed at every demise, relishing the over-the-top effects and the dark humor, while Hazel pointed out the plot holes and continuity errors. Emrys spent half the movie reading spoilers on his phone. Even armed with knowledge of what was going to happen, he watched the scariest parts through his fingers.

By the time the killer was revealed—improbably enough, the culprit was the comatose prom queen, who held supernatural sway over her classmates—it was well and truly dark outside. The sun had been hidden by clouds all afternoon, and at some point, it had sunk, unseen, below the horizon. The night, as black as the day had been gray, was lit only by irregular flashes of lightning and the yellow glow of electric lights on the street below.

None of them were prepared for the shrieking of the door buzzer, which cut through the night like a deranged prom queen’s cleaver, making bloody tatters of the quiet.

Hazel screamed, causing Serena to spill the popcorn (which was mostly buttery kernels by that point). Emrys fell right off the couch.

Serena slapped Hazel’s arm playfully. “You scared me!”

“Not on purpose!” Hazel squeaked.

“Who is it?” Emrys wondered aloud.

“It’s probably my brother,” Serena answered. “He forgets his keys all the time.”

Their apartments all had the same simple intercom system—a beige control panel with a speaker and three buttons, mounted on the wall beside each apartment’s door. Serena sauntered up to the panel and pressed the “speak” button. “Who is it?” she asked in a singsong voice. She pressed the “listen” button so that they could hear the reply.

But there was no reply.

She tried again. “Helloooo?” she said. “Dom, is that you?”

No answer. Just the low hiss of the speaker, and the faint staccato tap of rain on pavement. And maybe …

“Do you hear—?” Emrys began.

“Shh!” said Serena.

They all leaned closer to the intercom. The sound quality was so poor that Emrys couldn’t be sure, but he thought he heard …

Breathing.

Serena quickly pulled her hand away from the panel. “Did you guys hear that?” she whispered. “Someone’s down there.”

“Maybe it’s Dom, like you said,” Hazel suggested. “He’s probably messing with us.”

“Forget that,” Serena said, and she jammed the “speak” button. “Hey, weirdo!”

Emrys flinched. That word always stung like an insect bite.

“We don’t want any,” Serena continued. “Go bug somebody else, all right? Get lost!”

Emrys’s jaw dropped, and Hazel said, “Wow.”

Serena took her finger off the button and did her patented shrug-and-smirk combo. “That should take care of that. Now, can we please go finish the—”

A sudden burst of strobing light flashed in the windows, filling the apartment with searing brightness; a roaring crash of thunder followed quickly after, seeming to shake the whole building. They all yelped in surprise, then yelped again when the lights cut out and the apartment was plunged into darkness.

“Well, crap,” said Serena.

“I can’t see!” said Emrys. The dazzling flash of lightning had set his vision buzzing. He flailed about, accidentally smacking Hazel in the face.

“None of us can,” Hazel said, batting away his hand. “Give it a minute.”

There was a moment of absolute silence as they waited for their eyes to adjust. Emrys checked his pockets for his phone, then realized he’d left it on the couch.

And then the door buzzer, right beside them, shrilled loudly.

This time, Hazel didn’t scream. Or maybe she did, and Emrys simply couldn’t hear it. This close, the buzzer was so loud—he clapped his hands to his ears, desperate for the sound to stop, but it kept going in a long, uninterrupted shriek.

Suddenly, a light cut through the void. Hazel found her phone and activated her flashlight app, and now the entryway was lit in a harsh blue-white light. The shadows moved at severe angles as she swung the phone around to illuminate their surroundings. Emrys saw Serena pounding her fist against the intercom in a vain attempt to make it stop. When it became clear that wasn’t working, Serena gripped it with both hands—and ripped it off the wall.

The noise stopped immediately.