Nina found the first clue in her lunchbox, underneath a bruised pear and the sandwich she had asked her father not to make.
The paper was folded into a square so small it looked like a sugar packet. On it, in green ink, someone had written:
Our names are one bell late. MJCSBSZ. Thursday. 3:15.
There was no signature. There was, however, a greasy thumbprint that smelled faintly of orange peel.
“It’s a code,” said Kit, reading over her shoulder at the lunch table.
“It’s somebody’s idea of a code.” Nina put the note flat under her carton of milk. She had been at Bellweather School for thirteen days. That was long enough to know where the bathrooms were, and not long enough to be comfortable with anonymous invitations.
Kit wrote the letters on a napkin. “One bell late. Move each letter back one.”
M became L. J became I. By the time she got to the second S, Nina could see the word.
“Library,” they said together.
Across the table, Ari looked up from a drawing of a bus with six legs. “What happens Thursday at 3:15?”
“I don’t know,” Nina said.
“Then we’re going to the library.”
Kit folded the napkin into a pocket. “I have chess.”
“Today is Wednesday,” Ari said.
“I have chess every day in my heart.”
The library had two doors, thirty-six shelves, and a stuffed fox named Mayor Fluff who had lost one glass eye. If the code meant anything more than library, the note did not say. They searched for green paper between the books until Ms. Vale, the librarian, asked whether they were looking for a title or trying to re-shelve the whole room.
Nina showed her the note. Ms. Vale read it without smiling.
“I know where you can start,” she said. “The book that holds no stories but remembers every borrowed one is behind the desk.”
She brought out a battered green checkout ledger. Most books had been entered by computer for years, but Ms. Vale still wrote down the odd things children borrowed from her desk: a ruler, a chess board, the battery charger for the reading lamps. On the last page, three names appeared beside the same item: Kit, Ari, and Nina. None of them had signed it.
The item was ROOM 12 KEY. The return time was THURSDAY 3:15.
“Is someone allowed to borrow a room?” Nina asked.
“People borrow it all the time. It’s across from the art cupboard.” Ms. Vale closed the ledger. “The key stays with me. The entry is a clue.”
“You’re in on it,” Ari said.
“I am a librarian. I’m in on many things.”
The three went to Room 12. It was locked, but through the window they could see a table, a stack of cardboard boxes, and a paper sign turned face down. The room had once been a language lab. Now the school used it for things that did not quite have a home: spare music stands, two broken globes, a papier-mâché volcano with an alarming crack down the middle.
“Maybe it’s a club,” Kit said.
“Maybe it’s a punishment,” Nina said. “Someone put our names in the ledger.”
“Maybe it’s a club punishment.” Ari pressed his nose to the glass. “Those are the best kind.”
They found the second clue after lunch. It was taped to Kit’s chess board, which lived in Ms. Vale’s office because his little brother used it as a parking lot for toy trucks at home. This one said:
Three of you can open the door. Four can keep it. Find the person who knows where the rain goes when it misses the drain.
“That is a very bad riddle,” Kit said. “Rain can go anywhere.”
“The playground drain,” Ari said. “When it overflows, the water goes behind the bike rack. Jo knows. She drew the map for the caretaker.”
Jo was in the art room, making a clay cup with eight handles. She had drawn the puddle map because the big one soaked through children’s shoes on the way to the buses. She had also, she informed them, found a note inside her art folder that morning. Hers said only Don’t tell Nina it’s a prize.
Nina felt heat climb her neck. “Who said I thought it was a prize?”
“No one,” Jo said. “That’s why I didn’t tell you.”
“I didn’t think it was a prize.” Nina had, for about seven minutes, imagined winning a tablet. “Who wrote these?”
Jo shrugged. “The handwriting looks like Theo’s.”
Theo sat behind Nina in science. He could make a paper bridge hold a brick and could not remember to put his name on his homework. On Friday he had announced that the old language lab was being emptied because nobody used it. Nina had thought he sounded almost pleased.
They found him outside Room 12, trying to peel the tape off a cardboard box without tearing it. He stopped when he saw all four of them.
“You weren’t supposed to come until tomorrow,” he said.
“Your riddle led us here,” Kit said.
“It led you to Jo.”
“We found her,” Ari said. “Then we walked here.”
Theo gave the box a miserable look. “I should have made another clue.”
Nina held out the note from her lunchbox. “You put this in my food?”
“In your lunchbox. Before lunch. I washed my hands.”
“You could have asked us to come.”
“I did. In a way.”
“In the way where nobody knows what you’re asking.”
Ms. Vale came down the hall carrying the Room 12 key. She let them in, saying she would be at her desk if they needed her. The upside-down sign on the table read THE MASTERMIND GAMES. Below it, in smaller letters, Theo had written Members: 1.
There were games in the boxes, but no tablets and no gold cup. There was a bridge challenge made from paper strips, a board covered in misleading treasure-map symbols, and a little town of cardboard buildings with streets that could be rearranged. One box held a stack of old notebooks from children who had used the room years ago. They were full of sketches, failed codes, and enthusiastic exclamation points. On one page, a girl had written The secret is that we make the games for each other.
“Ms. Vale used to run it,” Theo said. “Before the computers went in. I found the notebooks when they started clearing the room. She said we could keep meeting here if four people wanted it, because then it’s a club and not just me borrowing a classroom.”
“Why us?” Jo asked.
Theo pointed to the town. “Ari sees how streets connect. Jo mapped the playground. Kit spots rules everyone else misses. Nina solved that thing with the science fair labels.”
Nina stared at him. A week earlier, when two projects had been switched, she had noticed that one label described a plant while the display held a motor. She had been accused of snooping until the owners sorted it out. “That wasn’t a game.”
“You worked out what happened. I thought you’d like this.”
“You thought,” Nina said. “You didn’t ask.”
Theo looked down at his shoes. “When I tell people I like puzzles, they ask me to do their homework. Or they ask what my score is on something. I wanted to find people who might just play.” He picked a fleck of orange peel from his thumb and dropped it in the bin.
Kit pulled out a chair. “I play chess badly. I like the part where you get surprised.”
“I got a prize for my puddle map,” Jo said. “It was dry socks from the office.”
Ari picked up a cardboard bus from the town. “This one has only four wheels. That’s a design failure.”
Theo laughed, a quick sound that seemed to startle him. Nina still disliked the note in her lunchbox. She disliked being chosen before she had a chance to choose. But she liked the town, and she liked that the notebooks contained as many crossed-out ideas as clever ones.
“If we’re making games,” she said, “we need a rule about clues. A clue has to give you enough to solve it. ‘Where the rain goes’ could be anywhere.”
“I knew Jo would get it,” Theo said.
“That’s because you already knew the answer.”
He considered this. Then he turned the sign over and wrote RULE ONE: OTHER PEOPLE GET TO UNDERSTAND THE CLUES.
“Rule two,” Jo said. “No putting things in anyone’s lunchbox.”
Theo wrote that down as well. Ari insisted on a third rule concerning buses with six legs. By the time Ms. Vale came back, the cardboard town had a river, three bridges, and an argument about where to put the bakery. The language lab still smelled of dust, but the table was crowded.
“Four?” she asked Theo.
He looked at Nina. She was holding a bridge upright while Kit moved the road. “Four, if they want to,” he said.
Nina said she would come Thursday at 3:15. She also wanted to design the next puzzle herself. She had an idea involving the cracked papier-mâché volcano, though it would need a better hint than Find the mountain. She wrote that down before she could forget it.