The square in Moon Street smelled of wet earth and fresh leaves. The rain had just quietened down and paper boats were floating in the puddles. Hania in her red wellingtons took careful steps along the kerb, counting snails. Olek carried a rucksack full of treasures: a magnifying glass, string, a slice just in case and a sultana cookie. "Look, the cloud looks like a whale!" - exclaimed Olek and pointed to the sky reflected in the water. "And that leaf over there looks like a heart," added Hania, picking up a shiny brown chestnut. The cat from the kiosk, called Noodle, stretched on the bench and squinted. Nothing seemed to interest him, but when a gust of wind rustled the vines entwining the large chestnut, the cat fluttered an ear. "Ding," it sounded softly. Once. Then a second time, as if someone was making a very polite invitation. "Did you hear that?" - whispered Olek. Hania nodded. "It wasn't a swing. The swing creaked, and it sounded like a bell." The children walked up to the roots of a large chestnut tree. The vines were thick, the leaves wet and cool. Hania opened the green curtains and almost jumped back in surprise. Behind the leaves was a tiny blue door. So small that a larger rabbit would have to bend down. A brass star glittered in the middle of the door, and to the right hung a golden bell on a silver thread. At the foot was a felt doormat with the words: "Please knock or ring". "The door!" - whispered Hania. "Right here, in the middle of the square!" "Who could have made them?" - Olek knelt down and looked closely. He scrunched up his nose. "Maybe there are... um... artist ants living here?" "Or someone very tiny and very kind," Hania added, pointing to the doormat. "Ding," the bell sounded, although no one touched it. Macaroni the cat jumped off the bench and squatted next to it, staring at the door as if it were a television. Hania looked around. The square was empty. Mrs Zosia from the newsagent was stacking newspapers, and in the distance a blackbird was rolling in the wet grass. Only the door seemed to be waiting. "Shall we call?" - Olek asked. "We need to say hello first," - said Hania seriously. She arranged a small gift next to the doormat: a shiny chestnut and a yellow leaf in the shape of a star. Only then did she grab the silver thread. "Good morning!" Bell sang warmly: "Ding-a-ding-a-ding". At the same moment, tiny circles appeared on the surface of the nearest puddle, as if someone had scattered a handful of beads over the water. "Did you see?" - Hania opened her eyes wide. "The circles are making themselves!" - Olek stood up on his toes until he did. "It's a sign." They acted very carefully. Olek unfolded the magnifying glass, Hania smoothed the doormat. The cat Noodles puffed up his tail and stepped from paw to paw. They noticed a little chalk drawing on the blue paint of the door - a tiny arrow and next to it a tiny lock, in the shape of a leaf. When they looked closely, they found that the lock-leaf was different from all the others. It had five teeth and a tiny dotted spot. "We'll find one!" - Olek immediately set off between the vines. He searched, mused, looked under the bench, until finally he discovered something under his shoe that crunched like candy in paper. He picked up a leaf with five teeth and dots. "There it is!" Hania carefully applied the leaf to the lock. It fit amazingly well. It wasn't a normal lock - more like a small drawing of a lock, but when the leaf touched the chalk line, the line flashed as if it was made of light. "Oooo..." - slipped out of Hania's mind. "Shh, listen." - Olek adjusted his ear. From behind the door came a soft whisper, a little like the rustling of pages, a little like the purr of a kitten falling asleep. "Maybe someone is reading a book?" - guessed Hania. "Or counting crumbs?" The children crouched closer. The smell of cocoa and... something else could be smelled in the air. Like the smell of freshly tempered crayons mixed with the aroma of warm bread crust. The bell was silent, but the grass around the door floated slightly, as if breathing. Olek opened his backpack. "We have a gift for friendship." He took out a sultana cookie and broke it in half. "Half for us, half for... well that's it." He placed half on a leaf next to the doormat. "Here you go." "Another piece of paper!" - Hania quickly plucked a small piece of paper from her notebook and wrote in big letters: "Good morning. We have a magnifying glass, a willingness to help and good manners. Hania and Olek." Slipping the note under the doormat, she added: "And Macaroni the cat." Noodles muttered as if to say: "Of course." Suddenly the breeze quieted completely. The drops on the vines stopped trembling. Even the blackbird in the distance stopped whistling. It became calm and a little... quiet, until one reflexively held one's breath. "Ding" - the bell rang out in a single, low tone. Then again. And more. Under the doormat, something brushed the paper. Hania's card slid slightly, as if it had been pulled inside. In its place something else appeared: a fine silver hair, like from the mane of a windmill? No, it was a thin thread, shimmering like a morning spider's web. "Is that an invitation?" - Olek tilted his head. Hania touched the thread with her fingertip. It was warm. "I think so." As soon as she said this, the door vibrated slightly. As if someone on the other side had lifted the latch. The brass star flashed and the grass around it trembled. Olek bit his lip. Noodles murmured warningly, but did not run away. "Hold the key-leaf," whispered Hania. Olek placed the leaf on his hand. His heart was beating as if it were rhythmically knocking on a small eardrum. The children leaned in, so close that they could count the tiny knots in the blue wood. The bell was silent, only the thread moved gently, like the hand of a miniature clock. Something murmured a little louder. Like several voices at once, like the splashing of a teaspoon in a teacup. And then... the handle moved from the inside, first a little, then more. The leaf-shaped lock lit up with a soft glow, and a luminous line danced across the blue door, straight towards Hania's hand. "Oh my..." - whispered Hania and held her breath. The handle vibrated once more, slowly, slowly, until finally it began to turn