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

It rolled across the Green to the mending shed and bumped the bell on the door. One ring. One ring means something is broken.

Above the bell, an old crack in the door frame had been filled and sanded. Someone had scratched a tiny hammer beside it.

Beto's aunt ran the shed. She was out at the market, but she had left a note on the bench.

Mrs Ortiz's camping lamp. Won't light. Back at four.

Beside the note sat a green camping lamp with a handle. Beto clicked its switch. Nothing.

"How does it work?" said Beto. "I could take it apart."

"Can I help?" asked Lan.

"In a minute," said Beto. He did not look up.

An armadillo with a little meter trundled out from under the bench. His name was Push.

"Check the push before you blame it," said Push.

Beto opened the battery door. Three batteries sat in a row.

Push touched his two thin probes to the ends of each one. The number blinked awake.

"One and a half volts of push," said Push. "Three times. Three in a row add up. Four and a half."

"So the batteries are fine," said Beto.

"The push is there. Something else is wrong," said Push.

Lan held out her hand for the tester. Beto put it in his own pocket. Lan's hand dropped. She sat on the stool by the door and said nothing at all.

Beto screwed in a new bulb from the drawer. He clicked the switch. Nothing.

"Forget it," he said. "It's rubbish. Mrs Ortiz can buy a new one."

He picked up the lamp and turned towards the bin.

A river otter in a bright orange vest hopped onto the bench. Her name was Flow.

"Find the gap first," said Flow. "No loop, no flow. Electrons need a road home."

She clipped a little test lead to the battery. "Follow it all the way round," she said.

Battery to wire. Wire to switch. Switch to bulb. Bulb back to battery.

At the battery, the lead beeped. At the switch's first screw, it beeped. At the second screw, silence.

Flow pointed a paw. "Here's where it stops."

Inside the switch, one thin wire had slipped out from under its screw. The road had a gap in it.

A bowerbird in a vest full of small pockets landed beside Flow. That was Build.

"Every part has one job," said Build. "This wire's job is to carry the current across the switch. Let's give it its road back."

She showed Beto how. Strip a little plastic off the end. Twist the copper strands so none stick out. Tuck the wire round the screw the way the screw turns.

"Snug, not squashed," said Build. "Talk to your parts. They like it."

Beto tightened the screw. The loop was whole again.

He reached for the switch. Then he stopped. He looked at the stool by the door.

Lan had not spoken for an hour. It felt like a very long hour.

She went first. "I wanted a turn with the tester," she said. "I know what the numbers mean. You never let me."

Beto's face went warm. He was going to say it's my aunt's shed. He didn't.

"Sorry," said Beto. He took the tester out of his pocket and held it out. "You test them. I'll write the numbers."

Lan touched the probes to each battery. One and a half. One and a half. One and a half.

"Four and a half," said Lan. "I'll do it!"

Beto clicked the switch. The lamp came on, warm and yellow, all over the dusty bench.

Flow did a little spin. Push gave one slow nod. Build was already telling the switch it had done very well.

At four o'clock Beto's aunt came back. She put the battery tester into Beto's tool roll. It was the first tool in there.

Back on the Green

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

That evening Lan's bike light flickered and went out. She did not throw it away.

She opened the little door and followed the road all the way round, with Beto holding the torch.