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

It rolled through the gate of Brightfield School on an ordinary Tuesday. It was poster day. Each group had to make a poster about the river trip. Nothing big happened. Only one small thing, at the big table by the window.

The big table had a patched top. In one corner of the patch was a tiny hammer.

This is how Lan told it.

"Inkling grabbed the poster and did all the drawing. The ducks, the reeds, the sky, everything. There was nothing left for me. I just sat there. She's such a show-off."

She told it to Manywhy after school, with her arms folded.

"That's one thread," said Manywhy. "Are there more?"

"No," said Lan.

"Never stop at one reason," said Manywhy. "Let's hear it from the whole group."

How much did it hurt, really? Lan put the dial at: a lot.

This is how Inkling told it.

"On Monday we split the jobs. Beto got the title. I got drawing. Someone else got the facts. Lan wasn't there, so she didn't get a job. I thought she didn't want one."

"I didn't know she minded," said Inkling. "I was just doing my job."

Inkling put the dial at: hardly anything. Then, seeing Lan's face, a bit more.

This is how Beto told it.

"Inkling had the good felt pens from home. The really bright ones. So of course she did the drawing. And Lan was off on Monday with a cold."

Beto put the dial at: not much. He had been busy with the title.

A boy with round glasses and a grey sweater had been sharpening pencils at the back. His name was Lint. He had small tweezers in his pocket, and a sly, friendly grin.

"Ah, but wait," said Lint. "The pens. That's true. But is it a cause?"

"What do you mean?" asked Lan.

"Pull it out and see if anything changes," said Lint. "If Inkling had used the class pens, would you have had a job on the poster?"

Lan thought. "No. I still wouldn't have had a job."

"Then it's real, but not the reason," said Lint. He mimed pulling a bit of fluff off his sweater with the tweezers. "That's fluff, not thread."

A girl with a long dark ponytail and a rust-coloured sweater was sitting on the windowsill with an old brass balance scale. Her name was Fulcra.

"Let's weigh them," said Fulcra.

She held up the scale. "In this pan: Inkling likes drawing. In this pan: the jobs were given out on Monday. And Lan was off sick on Monday."

She tipped the scale gently to one side. "This side tips. Not only. Mostly. The jobs were split on the one day Lan wasn't there. Nobody saved her a job."

"So it wasn't Inkling grabbing," said Lan slowly.

"Mostly," said Fulcra, "it was a Monday cold."

Rheo, the boy who ran the lights for the school play, held out the paper dial.

"Not a switch. A dial," said Rheo. "How much was it, really?"

Lan turned the arrow down. Past a lot. Past the middle. To a little.

"I was off when the jobs were given," she said. "That's mostly it."

Their teacher was marking books at the next table. Lan went over to Inkling, who was colouring the sky.

"Can I do the captions?" asked Lan. "Under the pictures?"

Inkling slid the poster across at once. "I'm terrible at neat writing," she said.

Lan wrote the captions in her best pencil. When they pinned it up, the poster had two kinds of handwriting on it.

Back on the Green

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

The next time Lan was off school, she asked Inkling the next morning: "What job did you save for me?"