SHE WAS ON THE STREET OUTSIDE THE POST OFFICE BUILDING.

Above the post office, the sky was smeared blue. On either side, the buildings were blurry, as if she were seeing them through cloudy glasses. All the windows were gray. She didn’t know why she was here. Did she have to mail a letter? She opened the door to the post office . . .

Inside was a classroom. Back to the door, the teacher was writing on the chalkboard, and Sophie remembered in a rush: watching the dream in the somnium, sitting on the floor with Monster, drinking the bottle. But in the somnium, the teacher appeared at the end of the dream. She was messing up the order. She was supposed to find the winged ponies first.

Shutting the door, Sophie jogged away from the post office. The houses were indistinct smudges on either side of her. She craned her neck, looking for the white house with blue shutters. The street was silent. No cars, no buses, no bikes.

Behind her, she heard footsteps.

Glancing over her shoulder, she saw the teacher. His face was only a mouth. No eyes. No nose. He spoke: “You cannot escape me.”

His mouth began to open, wider and wider, and the post office was sucked into his mouth. A few buildings followed, like a painting ripped from a wall. This wasn’t what was supposed to happen! She must have changed the dream.

Sophie ran.

Ahead was the white house with blue shutters. She heard a whooshing sound, like water going down a drain. Don’t look. Just run.

She threw herself at the door. Yanking it open, she glanced back. The teacher’s mouth had stretched impossibly wide, and the street was flowing into it like a river. She jumped through the door and shut it behind her.

The door promptly disappeared.

She was in the clouds. Sophie exhaled. She didn’t think he could follow her if the door was gone. And the teacher hadn’t been in this part of the dream. Only the winged ponies. She was safe. Maybe.

Harp music played, chords plucked at random, no clear melody. All around her, pink fluffy clouds drifted into the shapes of castles and trees and mountains. She was standing on one cloud, and a rainbow unfurled over her head as if it were a ribbon tossed through the air.

Monster would hate this, she thought.

Several winged ponies flew between the clouds, a rainbow of pastel colors: pinks, purples, baby blues, above the real rainbows.

“Hello?” she called to the ponies. “Can any of you help me? I need help!”

One of the ponies paused midflight. “Who calls for help?” His voice was as deep as a foghorn. Leaving the herd, he flew toward her. His hide shimmered as if he’d been painted with glitter, and he had a silver unicorn horn spiraling up from the center of his forehead. “Oh, my, it’s a damsel in distress!”

“I need—” she began.

Flapping his wings, he rose higher. “Come with me,” he commanded. “The others must hear your words.”

“But I can’t fly!”

“Use the rainbow.” He pointed with his horn at a rainbow that kissed the nearest cloud.

He couldn’t mean she should walk on the rainbow, could he? She’d fall! Except she wasn’t falling through the cloud, and this was a dream . . . Crossing to the rainbow, Sophie tapped the yellow band with her foot, and her toes sank into the colorful mist. She tested putting weight on her foot—and it held. Taking a deep breath, she climbed onto the rainbow.

Ahead of her, the winged pony trumpeted, “Assemble, my friends! There is a damsel in distress!” He whinnied loudly and flicked his tail to catch the attention of the other ponies. “Attend to me!”

Several ponies circled closer, flying around the rainbow. A few of them had unicorn horns; a few didn’t. One had flowers braided into her mane. “How can we aid you, Damsel?” the pony with flowers asked. She had a voice like a wind chime, light and tinkling.

Quickly, Sophie explained everything as best she could: about herself, about the Dream Shop, about her parents, about the missing kids, and about Mr. Nightmare.

When she finished, the ponies turned to each other, whickering and whinnying. She heard one say, “I am not a dream. Such lies! Such nerve!” Others echoed her.

One by one, they took flight. Plucking at the top of a cloud tree, one pony swallowed a mouthful of pink cloud before flying away. Another dived inside a cloud castle, and the drawbridge (made of clouds) shut behind him with a poofing noise. The pony with flowers snorted at Sophie and then flew up toward the sun.

“Wait! Please! It is true, I swear!” Sophie called after them. “And after it’s over, I promise I’ll send you back into a dream.” This had to work! She was risking so much . . . “Come back!”

At last only the glittery unicorn remained. Lowering himself onto the rainbow beside her, he sniffed her hair and puffed air in her face. “I have often wished for a quest of my own. Please, tell me more, Damsel. What would I have to do to complete this implausible task?”

She took a deep breath and told herself it wasn’t over yet. She needed only one pony. “You have to come with me out of the dream, and then fly me and my friends to a particular house and then back safely, without being seen.”

“And what will be my reward?”

She had no idea what a winged unicorn who lived in a world made of fluffy clouds would like. She’d never even ridden a regular horse. She’d read a few girl-with-horse books—one showed a girl giving an apple to a stallion on the cover. “An apple?”

He considered it. “Indeed, that would be most—”

Before he could finish, the rainbow beneath them evaporated. Sophie plummeted. Wind tore at her as she clawed at empty air. She felt as if her whole body was screaming.

“Dive, Damsel, dive! Down into the foam, down in the briny deep!” the iridescent unicorn cried. “Down to our destiny! Dive, my brave friends!” He flattened his wings to his sides, and dived straight down toward the sea. Other ponies dived around him.

No, no, no! She knew this part of the dream—below was the ocean, and once they splashed down, she’d be in the classroom with the teacher. The dream couldn’t end yet! He hadn’t said yes. “Come with me!” she called. She didn’t know if he could hear her.

The ocean rose toward them. The ponies hit the waves one after another as the clouds tumbled around them, the castle falling apart. Then she was in the foam, and the waves crashed over her head, and the ponies had all disappeared, as if they’d dissolved into the surf. Water poured down her throat and—

She sat in a classroom. The teacher was at the blackboard. In chalk, he’d written: You cannot escape. Jumping to her feet, Sophie ran toward the door. She had to reach it before the teacher turned. Lunging for it, she yanked it open—

And there was nothing there. Vast emptiness before her.

A hand clamped onto her shoulder. She spun around, and the eyeless teacher opened his mouth wide. She screamed and threw her arms in front of her face—