The puddle was enormous, shimmering like a silver plate in the middle of Maple Street after the rain. Clara stopped to look at it. It was perfectly flat, perfectly still, and deep — deeper than a puddle had any right to be. She could not see the bottom.
She crouched beside it. The sky reflected in the water, blue and wide and full of clouds. But something was wrong. The clouds were moving the wrong way. They drifted from west to east, backward, like the whole world had turned itself around in the puddle's surface.
Clara leaned closer. Her reflection looked back at her. Only her reflection was smiling. Clara was not smiling.
"Hello up there," said her reflection.
Clara fell backward onto the wet pavement. The reflection had spoken. Not in a squeaky cartoon voice, but in Clara's own voice, clear and calm, as if talking to yourself in a mirror was the most ordinary thing in the world.
"Don't fall over," said the reflection. "You'll miss the window."
"What window?" said Clara.
"The one that closes," said the reflection. And it reached up, out of the water, and pulled Clara in.
The world turned upside down. Clara tumbled through cool liquid that did not get her wet. She landed on something solid with a thump and opened her eyes.
She was standing on the ceiling.
Above her, the sky hung in a puddle. The real sky. The one she had just fallen from. Trees grew downward from the ground above, their roots pointing at her like bony fingers. The houses of Maple Street were there too, but they were upside down, their roofs stuck into the dirt and their foundations waving at the clouds.
Clara was in the Upside.
A girl stood in front of her. Same curly hair. Same gap in her teeth. Same purple rain boots with the scuffed left toe.
"Welcome," said the other Clara.
"You're me," said Clara.
"The opposite me," said Opposite Clara. "Here everything is the same but backward. You're brave. I'm cautious. You love pancakes. I love waffles. You laugh at sad parts in movies. I cry at funny ones."
Clara stared at the upside-down houses. A cat walked along a fence that was somehow below her and above her at the same time. It was Mrs. Marconi's orange tabby, but it was walking upside down on the bottom of the fence, its fur pointing the wrong way.
"The puddle," said Clara. "I have to go back."
"You can't," said Opposite Clara. "Not until the puddle dries up. Then the door closes forever."
"Then I'll go now," said Clara, and she jumped toward the puddle in the sky above her.
But she did not go up. She went down. Here, up was down and down was up, and the puddle was not where it used to be.
"That's the first rule," said Opposite Clara. "The door moves. Every time it rains here, a new puddle opens somewhere. And the old one closes."
Clara looked around. The sky was perfectly clear. Not a cloud in sight. If it did not rain soon, the puddle she had come through would evaporate and she would be stuck here forever.
"How long?" said Clara.
"An hour. Maybe two," said Opposite Clara. "It's a small puddle. You jumped in on a sunny day."
Clara's heart hammered. "How do I find it?"
Opposite Clara pointed to a streetlamp that grew up from the sky above them. On its side was a map. Clara scrambled over a mailbox (upside down, so she had to climb under it) and reached the streetlamp. The map showed Maple Street, but backward. Every landmark was flipped. Mrs. Marconi's house was where Mr. Chen's house should be. The big oak tree was on the wrong side of the road. And the puddle — her puddle — was marked with a tiny blue circle at the far end of the street.
"It's moving," said Opposite Clara. "Every ten minutes, it shifts to a new spot. You have to catch it before it dries up."
Clara looked at the map again. The blue circle was at the corner of Maple and Pine. But across town, dark clouds were gathering. It was going to rain in the Upside.
"If it rains," said Clara, "a new puddle opens. But I need my puddle. The one I came through."
"Yes," said Opposite Clara. "Your puddle is the only way back. A new puddle here opens to a different place. You'd end up in someone's bathtub in Brazil."
Clara did not want to end up in a bathtub in Brazil. She started running.
In the Upside, running was different. Every step pulled her forward, but her hair flew toward the ground and her boots made a squelching sound on the ceiling-sky. She passed upside-down mailboxes. She passed upside-down cars stuck to upside-down driveways. She passed a dog that chased a ball by throwing it upward with its mouth.
She reached the corner of Maple and Pine. The puddle was there, shimmering on the ceiling of a bus stop. She could see the real world through it — the sunny afternoon, Mrs. Marconi's cat napping on a porch, the familiar sight of home.
Clara jumped.
She did not go through. She bounced off the puddle like it was made of rubber and landed on her back, staring at the upside-down sky.
"It's closed?" she said.
"It moved," said Opposite Clara, who had followed her. "You were too slow."
Clara checked the map again. The blue circle was now at the other end of the street, near the school. She ran again, her boots pounding against the sky-ceiling. The clouds in the distance were closer now, fat and gray and promising rain.
She reached the school. The puddle sat in the middle of the upside-down playground, glinting. But it was smaller now. Half the size it had been. The edges were shrinking inward, curling like a drying leaf.
Clara leaped.
Her hand touched the surface. For a moment she felt the warmth of the real sun. But the puddle shrank beneath her fingers, and she pulled back her hand just before it vanished entirely.
"No," she whispered.
Opposite Clara stood at the edge of the playground. "One more chance," she said. "The last one."
Clara looked at the map. The blue circle had moved one final time — to the very spot where she had first fallen in. The center of Maple Street.
And the rain was coming. She could hear it now, a distant rumble. If it rained before she reached it, her puddle would be gone, and a dozen new ones would open to a dozen wrong places.
Clara ran harder than she had ever run. Her legs burned. Her lungs ached. The rain clouds rolled closer and the sky grew dark and the first cold drop landed on her cheek.
But she reached the middle of Maple Street.
The puddle was there. Small, no bigger than a dinner plate, but still open. The real sky shimmered in its surface.
Without stopping, without thinking, Clara dove.
She hit the water and the world flipped. She tumbled through cool liquid and landed hard on warm pavement. Sunlight hit her face. The real sun.
The puddle beneath her was gone. Just a damp spot on the road, already drying in the afternoon heat.
Clara lay on her back, breathing hard. She was home. The real Maple Street. Mrs. Marconi's cat blinked at her from the porch. The real sky was blue and still and moving the right direction.
She sat up. She looked at the damp spot on the road. It was just a puddle. It had always been just a puddle.
But Clara knew better.
She stood up, brushed off her purple rain boots, and smiled. She smiled because her reflection in the window of Mrs. Marconi's house was smiling back at her. And for a moment, just a moment, her reflection waved.
Clara waved back.
Then she turned and walked home, stepping carefully around every puddle she passed. Not because she was afraid. But because you never know where one might lead.