The hammer rang once. A spark jumped off the anvil and did not go out. It waited. They followed.

It skipped across the Green and into the print shop. It stopped on the long table, next to a square of paper.

"Fold me, I won't mind," said Kami.

"Somewhere exciting," said Lan. "With something big happening."

"Then start with a fortune teller," said Kami. "Something that moves."

They folded the four corners to the middle. They turned it over and folded four corners to the middle again. They folded it in half and pushed their fingers into the pockets. A paper fortune teller.

The last crease went flat, and the paper opened like a door.

It was warm. That was the first thing. The air smelled of grass and salt.

They stood on a green hill, in the sun. Families sat on picnic blankets. People held binoculars. Far away across the trees, beside a bright blue sea, stood a tall white tower. Next to it was a white rocket.

"Japan," said Kami softly. "An island called Tanegashima. The date is the eighteenth of March, 1995."

On the nearest blanket sat a boy in a T-shirt. Next to him, a little girl in a sun hat was crying.

"I'm Ken," said the boy. "This is my sister Emi. She's four. There's a satellite inside that rocket, and it has a big flat panel, as big as a room. It's folded up small to fit inside."

"It will get squashed," sobbed Emi. "It will get all broken."

"I want to show her it won't," said Ken. "That something folded small can still open. But I don't know how."

"I'll do it!" said Lan. "I promise. Look, I'll make paper small." She grabbed a sheet from Ken's bag. She scrunched it in both hands, tight, tighter. A little paper ball.

"There," said Lan. "Small!"

Emi took the ball. She tried to open it. It was all crumpled and wrinkly. It would not lie flat. It would not move. It just sat there, a mess.

"It's broken," said Emi, and cried harder.

"Scrunching is not folding," said Mark. He had been watching from the shade of a palm tree. "A scrunch has no plan. Read the drawing first."

Lan looked at the crumpled ball. Her ears went hot.

"I promised before I checked," she said. "Sorry, Emi."

A little way off, a woman in a blue jacket stood watching the rocket. In her hands she held a small folded square of paper.

She did not look at them. She did not explain. But she pulled the two ends of her square apart.

It opened in one pull. The whole sheet spread out flat. Then she pushed the ends together, and it closed again, small and neat.

"Oh," said Inkling. "I noticed something. It knows how to open."

Mark went closer and looked at the lines printed on her paper. Dashes, and dashes with dots, in a careful zigzag pattern.

"Read the drawing before your hands move," said Mark. "The folds are in exactly the right places. So the folds decide how it moves. Fold where the lines say, and paper becomes a machine."

"Corners first, always," said Cornelia. "Bring every corner to the middle. Exactly."

She took a fresh square. She brought one corner to the middle, then the next, then the next, then the last. Four corners, meeting in the centre like four friends.

"Now turn it over," said Cornelia. "And do it again."

Four new corners went to the middle.

"How many flaps?" asked Ken.

Inkling counted, touching each one. "Four, and four more. Eight."

Ken folded the paper in half and pushed his fingers into the pockets underneath. He pushed.

It would not move. Something caught inside.

"It's stuck," said Ken. "It's broken too."

"It's stuck because one corner went past the middle," said Inkling, peering at it. "Look, that one pokes over."

"Crooked is just a first go," said Crinkle. "Smooth it out and try again. The crease remembers."

Ken opened that corner gently. A faint line showed where it had been. He folded it back, this time exactly to the middle, not a hair past.

"Hold it still," said Presso. "Now press it flat. Run your thumbnail along every fold."

Ken pressed. He pressed every fold, slowly and hard.

"A soft fold flops," said Presso. "A pressed fold is a hinge. It springs back the same way every time. A fold you press is a fold that stays."

"Every fold makes me something new," said Kami. "Now work it. Thumbs and fingers in the pockets. Push together, then pull apart."

Lan had made fortune tellers at school. She showed Emi how, one thumb or finger in each pocket. Emi put her small fingers in. She pushed. The paper opened one way, like a beak. She pulled. It opened the other way.

Open, close. Open, close.

Emi stopped crying. She started laughing.

"It's folded small," she said. "And it still opens!"

Just then, a great rumble came across the trees. The rocket rose on a long white trail, up and up into the blue sky, until it was a tiny bright dot.

Emi waved her paper machine at it. Open, close. Open, close.

Lan found a plain square in her pocket. They unfolded it flat, and the door closed behind them.

The spark dimmed to a warm dot and settled back on the anvil. The Green was just the Green again.

Back on the Green

At the print shop, Lan's big map would not fit in her bag. She did not scrunch it. She followed its old creases, and it folded up small and neat.

Tell the story back to someone. What made the paper machine stick?