The Spring Cavalcade was so colorful in the city park, as if a giant paint palette had tipped over among the trees. Lemon yellow balloons wobbled, the smell of cinnamon pancakes swirled in the air, the band's drum thumped softly next to the fountain. Lili, Matt, and Borka gasped from three sides at once when the fair crier unexpectedly announced:

– Master Tobias will show the Chest of Secrets soon! But it only opens to the one who solves the signs!

On the stage sat an ornate, brass-cornered chest, like a sleeping turtle. Master Tobias stepped in front of it in a red vest with a spotted bow tie. Curious sparks jumped behind his glasses, making Lili immediately sure: something exciting was brewing here.

– Four signs hide in the fair – said Master Tobias. – If you put them in order, the key to the chest will appear, tinkling softly.

But when he reached for his pocket, he looked up helplessly.

– Whoops. I hung the key with the green ribbon here on the hook... – he poked at the screw hanging on the edge of the stage. – And it's not here. It disappeared.

The audience grumbled. Matt's hand clenched into a fist involuntarily, just as investigations begin in books. Borka was already stomping on the spot.

– We'll help – said Lili. – Clues are our favorites anyway.

– Right – nodded Tobias, and winked at the children. – The chest loves riddles. The first clue is on the stage.

Someone had drawn a spiral on the stage planks with chalk. In the four turns of the spiral were tiny signs: a fish, a leaf, a bell, and a shoe. In the middle stood three words: "Look for the lines!"

– Lines? – hummed Matt, and leaned over the drawing. – Meaning verse lines! – Lili's eyes lit up. – Four signs, four lines.

They set off. The fish laughed back at them from the fishing game booth. The leaf rustled on the decoration of the leaf-pressing stand. The bell glittered among tiny bells at the craftsmen's tent. The shoe lay on the shoemaker uncle's table, freshly waxed.

At every place, they found a paper strip rolled into a tiny scroll inside a vial, with a verse line on it and the sign's drawing in the corner.

The first read: "Colorful wire glints."

The second read: "Shadow dances in it."

The third read: "The ribbon winds."

The fourth read: "Lace window on its side."

– Look at the first letters! – whispered Lili. – C, S, T, L... We need one more line with T!

– T, like tent, and flag! – snapped Borka, and pointed towards the big circus tent, on the tip of which a flag was indeed waving.

Under the white-red stripes of the tent, a tiny paper bearing the print of a wooden stamp was fastened to the canvas with a needle. Matt pulled it out carefully. They found the missing verse line on it: "The flag flies."

Lili dotted the letters in the air.

– TENT – she said triumphantly. – The poem told us!

Inside the tent there was no performance. In the twilight, the gentle rustling of the canvas could be heard, and the smell of the ring's sand. On the background set, they found a pocket with another card inside. The card held a riddle:

"I have skin, but not an animal. If you pull, I smack. What am I?"

– Drum! – blurted out Lili and Matt at once.

– And look at the bottom! – Borka lifted it. – It is written there: "Look under me!"

The band played at the fountain. Uncle Jani, the drummer, lifted the big bass drum, smiling.

– Earlier something tinkled inside – he said. – I didn't dare fish it out, lest the rhythm fall apart.

Matt crawled under the drum stand and rummaged carefully. He pulled out a tiny tin box that resembled a miniature book. On top sat a fish sticker.

– Not the key – hissed Borka, then she was already smiling. – But surely a clue!

A folded map lurked in the tin box. It was a map of the fairground, with four red X's marking the locations of the fish, the leaf, the bell, and the shoe. The lines connected the signs and drew the shape of an arrow that pointed towards the shaded benches of the pergola. At the bottom of the map, in tiny letters, it read: "Under the striped shadow."

Under the pergola, the sunbeams fell, drawing striped shadows on the bench. Lili knelt down and peeked at the bottom of the bench. Just as one would do in a detective novel. Her heart throbbed a little from excitement.

– Something is hanging here – she said softly.

An improvised wind chime, made of spoons, colorful glass pieces, and a green ribbon, tinkled on the bottom of the bench. Caught on the edge of the green ribbon was a brass key, so shiny that even the shadow of the pergola reflected on it.

– Got it! – shouted Borka, and reached for it eagerly.

However, the key was tangled with the main string of the wind chime. Matt took out his shoelace and began to maneuver. Borka held the tiny glass pieces so they wouldn't tinkle away, and Lili loosened the knots as if stroking tiny snakes. One minute, two minutes – the key finally got free, and slid into Lili's palm.

– That's it! – Matt jumped up. – Back to the chest!

Many people were already gathering at the stage. Master Tobias scowled, but when he saw the key, his face shone like a freshly wiped copper plate.

Lili told them about the signs, the poem, the tent, the drum, the map, and the pergola.

– You are clever – said Tobias, and turned the key.

The lock yielded with a single soft click. The lid of the chest popped up, and no glittering treasures sparked within, but something even more pleasant: a bundle of old photos, tiny park seeds in a vial, and a roll of tissue paper with a story handwritten in calligraphy letters: "The diary of the park's oldest tree." Next to them colorful pencils, magnifiers, and postcards were placed.

– The Chest of Secrets guards the park's secrets – said Tobias. – Every year different children help open it. We always hide the key, but this year someone in the wind chime workshop was a little too clever with the green ribbons. – He winked mischievously at Borka, who still held a piece of green ribbon she'd untangled from the knot in her hand.

– So this was half game, half real mystery – muttered Matt, and glanced towards the drum where the tin box had been. – Such is the best.

– Whoever reads a little from the diary gets a seed too – nodded Tobias. – And can plant a secret. Because trees also solve puzzles: they read the letters of light, the news of the wind, the stories of birds.

Lili smoothed the paper gently. The first entry was about when the rope swing was put in the park. The second showed a photo of an old lady sitting on a bench, a puppy on her shoulder. In the third, the great flood was recalled. In the corners of the paper, tiny drawings were hidden: tiny leaves, shoes, bells, fish.

– These symbols were here all along – mumbled Lili. – We just had to learn to read them.

Master Tobias gave a tiny magnifier to each of the three children.

– For a keepsake – he said. – So you notice the next clue, wherever it pops up. Because there will always be a next one.

Borka pushed aside the curtain and looked out at the park. The wind lifted a red paper flag that fluttered just like in the poem. Under the pergola, a striped shadow lay on the bench, and the sound of the drum rolled across the promenade like distant waves.

– If something disappears next time, we already know where to start – she declared.

– At the signs – said Lili.

– At the knots – added Matt.

– And at the pancake – grinned Borka, because the scent of cinnamon sweetened the air like a forgotten secret. – You never know how many clues stick in the powdered sugar.

All three laughed, then they gathered around the chest, read and asked questions, and the park hummed around them like a foldable map being unfolded anew.