The moon hung over the Venters like a pumpkin patch - thick, golden and cut with clouds. Maple leaves lined the pavements like rustling carpets, and lanterns in the shape of cats, bats and smiling pumpkins looked out of the windows of the houses. At the market square, in an old, ivy-covered building with a cast-iron gate, all the windows glittered. This was the Ignatius Mermaid City Library, where Pumpkin Night was just beginning. Zosia, Kuba and Maks were standing in front of the entrance with torches hanging on their lanyards. Zosia, an eleven-year-old admirer of maps and notebooks, wore a headband with stars and a sequined cape. Kuba, a twelve-year-old inventor of homemade everything machines, dressed up as an explorer - with binoculars and an old compass from his grandfather. Maks, a year younger, had bat wings made of black felt that hooked on the doorknob every now and then. - A warm-up before the muffins," muttered Kuba, straightening his compass. - Mrs Aurelia promised prizes for the best team. The smiling librarian, Mrs Aurelia, had hair so grey that it shone like a spider web. Lurking on her shoulder was the brindle cat Papyrus, who knew how to jump off a chair without the slightest sound. - 'Good evening, brave Readers,' she said in a voice as soft as a blanket. - We are starting the Library Shadow Trips. There are clues waiting in each room. Please do not use phones. Torches will suffice, and keep your ears and eyes open. And remember: Books are like doors. Sometimes they lead further than you think. On a long table near the entrance stood pumpkins with letters cut out. Each one gave off an orange, pulsating glow. Zosia leaned over one, whose smile was slightly tilted. - 'Look,' she whispered. - The letters formed a password. 'K-A-T-A-L-O-G'. - She raised her gaze. - The old Card Catalogue. - The one with the wooden drawers that creak like an old door? - Maks ascertained, correcting the wings. - Exactly that one,' confirmed Mrs Aurelia. - Good luck, team 'Star Bats'. The corridors smelled of paper, dust and something warm, as if there was cinnamon tea hiding in the walls. Along the way they passed children dressed as wizards, cosmonauts and pirates. In places, garlands of black paper crows hung from chairs. A map of the sky hung from the ceiling, and lamps cast luminous spots as if someone had painted on the walls with a brush of fire. The old Card Catalogue stood in the corner of the Main Hall. It had row upon row of small drawers with brass handles, and tiny labels on them: 'A-B', 'C-D', 'E-F'.... When Zosia pulled one out, the wood squeaked. Then something tapped lightly inside, although her fingers had not yet reached the bottom. - Did you hear that? - whispered Kuba. - As if someone had called out.... with a drawer. Zosia carefully slid her hand in. From inside slid out a folded piece of paper tied with a blue ribbon and a small brass key in the shape of an oak leaf. On the sheet was a carefully drawn plan of the library. The lines were shaded, and in the corner someone had written in purple ink: "For those who hear books breathe." - See - Maks tapped his finger on the border. - There's an asterisk here, behind the 'Maps and Travel' section. - That is, in the Second Floor Room," Zosia reminded herself. - That's where the globes and those big atlases stand, which you have to open for two. They climbed the stairs, which creaked like pine branches. On the mezzanine hung a clock with a pendulum - as big as a window. It reflected the glare of the streetlight from the street, and its hands suddenly twitched and stood at 8:31 p.m. - Broken? - asked Kuba, tapping on the glass. The pendulum had stopped swinging. Silence filled the stairs, as if someone had turned off the sound. The map room opened silently. A row of globes shone like dark planets. A model of a whale hung from the ceiling, and engravings - mountains, rivers, caves and even cross-sections of volcanoes - hung on the walls. Papyrus ran between the bookcases, his tail sweeping the dust from the narrow path. - 'Behind Maps and Journeys,' muttered Maks, peering behind the lowest shelf. - 'Hey, there's a board sticking out here. Indeed, the back wall of the bookcase was slightly off. Sticking in the gap was a paper bat pinned to an old leather globe. The bat had a phrase written on its belly: "He who seeks the way, let him look where the pictures are silent." - "The paintings are silent - the Hall of Figures!" - exclaimed Zosia. - That's where the big, enclosed room at the end of the corridor is. The corridor to the other wing of the library was semi-dark and cooler than the rest. Luminous shadows ran across the carpet like the movement of water. The door to the Drawing Room was decorated with carved leaves. An oak leaf glittered above the handle - exactly like the one on their key. - Shall we try it? - asked Kuba. - 'The rules say that during the Podchody you can enter where the clues lead you. Zosia nodded and inserted the key. The lock clicked softly. The door opened into a wide, quiet hall full of tables with huge books lying around them. It smelled of starch, glue and something sweet. In the depths, under the window, stood an atlas so big it had its own supports. Papyrus hopped onto the table and gently nudged the atlas with his paw. The heavy cover swung open as if by a gust. The pages rustled like wings. A map of Windmills opened up - intricately shaded, with a river called Silent Copper and a market square marked. A warm, almost invisible glow flashed in the centre, right next to the library. - 'It's glowing,' whispered Maks, 'but how? Zosia puffed on the paper. A dotted line appeared on the cool surface that had not been there before. It led from the entrance of the library to the corner where there were no walls on the plan. Instead, someone had drawn a tiny tower with a triangular roof and written: "Clock Tower." - After all, our building doesn't have a tower," quipped Kuba, pushing back the compass. - It has an attic and an escape bell, but no one has seen any tower. A dried leaf slid out of the side of the atlas. Underneath it was stuck a ticket folded in half. Zosia unfolded it carefully. "Midnight reading - 31 October 1968." On the back, in pen, it said: "When the clock stops, open the door that is not there." - 'The clock has stopped,' Maks reminded quietly. At the same instant, all three torches dimmed, as if a cloud had passed over the batteries. Somewhere far away a teaspoon fell. The hall became quiet again. - The door that isn't there... - repeated Zosia and looked at the tilted wall behind the map bookcase. - There. They returned to the gap. When Kuba pushed the back board, it moved like a flap. Behind it waited a narrow space, and from it a winding stone staircase descended. They were cold and smooth, as if they had been walked on for many years, although no one mentioned them. - 'I feel a draught,' Maks remarked, 'and that means there's an exit somewhere. - Or an entrance - added Kuba and smiled uncertainly. - The three of us are walking. Together. They descended slowly, holding on to the railing. The wall smelled of dampness and lavender, like wardrobes storing old clothes. After a few flights of stairs, they saw a small platform and a metal door, without a handle, but with a narrow key. The oak leaf from their key flashed again as Zosia put it to the lock. The lock gave way, and behind the door they discovered an intimate chamber. It had a round window high up on the ceiling, through which a piece of the moon could be seen like a silver nail. In the corner stood a wooden box with plain sides, with carved leaves and small moons. On the lid someone had carved the words: "The library is listening". - Listens to what? - Maks asked, standing on tiptoe. - 'Maybe the ones who talk to her,' wondered Zosia. - Or... The box vibrated slightly, as if the air inside had moved. The torches dimmed even more. A narrow ray of orange light seeped through the gap between the lid and the side, soft as the flame of a candle hidden in a pumpkin. - 'Watch out,' warned Cuba, placing his hands on the lid. - 'I'm opening it slowly. From downstairs, somewhere in the corridors, came the muffled voice of Mrs Aurelia: - Dears, muffin break in five minutes! Please return to the Main Hall! The three friends looked at each other: the break was tempting, but their hearts were beating faster. Zosia nodded. - Quickly. We'll take a look and come back. Cuba lifted the lid a millimetre. The ray of light became a ribbon that circled his fingers like warm smoke. At the same moment, the door behind them moved noiselessly and slammed shut with a metallic click. The papyrus that had slipped in with them swished its tail, and a shadowy silhouette began to grow on the wall beside the circular window - not their own, composed as if of rippling, whispered sentences. Inside the box, something moved more distinctly, as if a very large, very old page was being turned....