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

There were three of them that Thursday. Inkling was eight and noticed things. Beto was nine and took things apart. Danya was twelve and asked how anyone knew anything.

The spark rolled down the lane behind the print shop, and the lane became a street of shops. Every window held maps. Rolled maps, folded maps, a map of the sea painted on a door.

A brass sign said CHART STREET. One corner had cracked off once and been riveted back on. Beside the rivet, Inkling noticed a tiny scratched hammer.

An envelope was pinned to a lamp post. It had their names on it.

Danya read it out. "Your globe is ready. Collect it from our shop at C4. We are three hundred metres north of the fountain."

A map was folded inside, with a grid of letters and numbers.

"Easy," said Beto. "Which way is the shop?"

Nobody on Chart Street had heard of it. A woman selling sea charts shook her head. So did a boy with a cart of compasses.

"How do we know the shop is real?" asked Danya.

"Because somebody wrote to us," said Inkling. "I noticed the stamp. It's from this street."

Inkling looked at the grid. "I can name it," she said. "4C. Fourth row down, third column."

She set off at once.

"Wait," said Plot.

A pangolin sat on the step of a map shop. Her scales had a pattern of tiny squares, like a grid.

"C4 is not 4C," said Plot. "On a grid like this, the letter comes first. Along the corridor, then up the stairs."

Inkling stopped. Her face went warm. She came back.

Plot did not point. She folded her claws and waited.

Inkling put her own finger on the letters along the bottom. A, B, C. She held it there and climbed the numbers at the side. One, two, three, four.

"C4," said Inkling. "And it's the fountain. There's no shop in it."

"So the shop isn't in C4," said Beto. "The fountain is. The letter said north of it."

"Three hundred metres," said Danya. "That's a long way. Or is it?"

A field mouse popped out of a map drawer. She had a folded map tucked in her waistcoat.

"What does that say?" asked Inset. She pointed to a little striped ruler printed in the corner.

Beto bent close. "One centimetre is a hundred metres."

Inset said nothing more. She sat on the edge of the drawer and swung her feet.

Someone had drawn a faint pencil line from the fountain, going up the map. Beto laid his pencil beside it and pinched the length between finger and thumb. He held the pinch against the striped ruler.

"Three centimetres," he said. "So that's three lots of a hundred metres. Three hundred."

"Small on paper," said Inset, "and?"

"Far on foot," said Beto.

Beto held the map out and turned towards the top edge. "North is this way," he said.

He pointed straight at a wall of shops.

An old tortoise with a brass compass on a cord stepped slowly into the street. He did not take the map.

"Where is the morning sun?" asked Bearing.

That was all he asked.

The sun was low and bright behind them. Beto looked at the map again. The little arrow said N, and it pointed at his tummy.

"The sun comes up in the east," said Beto slowly. "So east is behind us. So the map's east edge should face behind us too."

He turned the map round until the east edge of the paper faced the sun. Now the fountain on the map lined up with the real fountain, and the N arrow pointed up the street.

"I had it upside down," said Beto.

"Most people do, the first time," said Bearing. "Now it agrees with the street."

Try the Packet now, if you have it. Then read on.

Danya stood at the fountain. He did not trust a guess.

"How do we know we're there?" he asked. "We count."

He took long steps up the street, north, the way the map now pointed. Inkling counted out loud. Beto watched the shop numbers.

Two hundred and ninety-eight. Two hundred and ninety-nine. Three hundred.

A narrow blue door. In the window, a globe the size of a pumpkin, with a tag that said: FOR THE COMPANY.

The shopkeeper laughed. "Everyone walks to 4C," she said. "Then they hold the map upside down. You did both, and then you checked."

She gave them a small brass key from Chart Street, and they put it on a ring.

The spark rolled back up the lane, and the lane was just the lane behind the print shop.

Back on the Green

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

Inkling drew a grid on the back of a seed packet. She hid a pebble in one square of the school garden.

"Find it," she told Beto. "Column first, then row."