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

The spark led them to a cool patch of grass by the pond. Then it simply waited there.

Warm wind blew the Green away, and the ground under their feet was somewhere else, the day before.

They were standing at the edge of a wide green marsh. Reeds rustled. Ducks paddled in brown water. Beside the water stood a little village of wooden houses, and every house stood up on tall wooden posts, like a heron on its legs. One old post had cracked and been bound with a thick twist of bark, and above the binding Inkling noticed a tiny scratched hammer.

A boy about Lan's age was pulling a rope. On the end of the rope was a huge oak log, as long as a bed.

"It's the new post for our house," he said, puffing. "It has to come from the forest. The autumn rain comes tomorrow. Then the forest path is under water."

"I know what you need!" said Lan. "It's easy. It has a name! I promise, you just need a..."

The word came out wrong. It came out as a buzz, like a bee in a jar. Bzzz, bzzz.

The boy stared at her.

"It's the door again," whispered Inkling. "You can't bring the answer. You can only bring the question."

Lan's face went hot.

They tied the log onto a flat board. Then all six of them pulled: Lan, Inkling, the boy and three cousins.

The board scraped. It dug into the soft ground. Mud piled up in front of it. It barely moved at all.

They pulled until their hands were sore. They had gone ten steps.

Inkling did not try to name it. She lay down on her tummy and looked along under the board.

"What is touching the ground?" said Inkling. "All of it. The whole flat bottom. All of it rubbing at once."

The boy's cousin had an idea. They laid short round logs on the path and pushed the board on top of them.

It rolled! The board went sailing along. They all cheered.

Then a log popped out at the back. Somebody had to pick it up and run it round to the front. Then another. Then another.

Soon half of them were carrying logs instead of pulling. Three were pulling. Three were running. They were all out of breath.

Inkling watched a roller turn under the board.

"I noticed something," said Inkling. "Look, it only touches the ground along one thin line. And it turns instead of rubbing."

She thought a bit longer, the way she was learning to.

"I can name it now," she said. "A round thing rolls where a flat thing drags."

In the evening, grey clouds came up over the hills. The log was still halfway along the path.

They were too tired to run with the rollers any more. Lan sat down on the log. "It's hopeless," she said.

Then Lan remembered the door. She could not bring the answer. But she could bring a question.

"The rollers keep getting left behind," said Lan. "Could the round thing come WITH us?"

The boy looked at her. Then he looked at the rollers. Then he ran for his father's axe.

He cut two thick round slices from a log, like two big wooden coins. He made a square hole in the middle of each. He pushed a strong stick through both, so they turned together. He tied the board on top.

Now the round things stayed under the board. Nobody had to carry anything.

They pulled. It rolled. It rolled all the way to the village.

The post stood in its hole before the first drop of rain. The boy rolled his two wheels up and down the path, just for fun, laughing.

Nobody would ever write down his name.

Warm wind blew the day before away, and the grass under their feet was the Green.

On the side of the anvil, beside the D, there was a new letter. A small round O.

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

Back on the Green

Lan's little brother Tí had a toy truck with a wheel missing. Lan made a new one from a bottle top and a pencil. It rolled across the kitchen floor.

Tell the story back to someone. Why did the flat board drag? Why were the rollers not quite right?