The rain tapped on the tall windows of the Municipal Library No. 7 like drums. The narrow streets of Brzeziny smelled of wet bricks, and inside the library it smelled of dust, apples from the reading window and something else - something like electricity before a storm. Lena slipped off her hood and shook the water out of her hair. She was eleven years old, a nose after her mum and a collection of funny bookmarks she made from tram tickets and leaves. Maks, her cousin who was a year older, took off his backpack and looked around the room as if it were a game set. He knew how to fix anything made up of buttons, springs and screws. Neither of them had plans for such a wet Saturday, so when the Polish teacher wrote that the library needed hands to help with the clean-up, they came without hesitation. Sitting at the adult desk was Mr Wisniewski - a librarian with a perpetually untied shoelace and a peplum jumper. He had a smile that said he understood jokes, and eyes that said he had seen a lot of things in this library that no one writes about on the posters. - Well there you are, you scouts - he greeted them. - Big move today. The card catalogue from the annex to the new cupboard, and in the process... - here he looked at the clock with the big face above the door - ...we're going to try to tame that old man. He's a whole eight minutes late. The clock ticked like someone who can't decide whether to take a step or step back. The second hand trembled, but the hands seemed to be held by the air by their elbows. - 'Are we... - Maks began - ...supposed to do anything about the clock? - Not yet. 'The catalogue first,' replied Mr Wisniewski, and nodded at them to follow him through a heavy door marked 'Warehouse'. - It's an old cupboard with drawers. A born labyrinth. Be careful, because drafts like to cut numbers in this annex. The storeroom was long and semi-dark, and the light from a lamp suspended from the ceiling drew skins of shadow on the spines of books. In the corner murmured Cat Blob - an ink-black library cat with a white spot under his chin. He ran under their feet and jumped onto the top of a large wooden cupboard full of drawers with brass handles and label windows. - 'It's a card catalogue,' said Lena in awe. - A real one. - Exactly right, Miss Lena - nodded the librarian. - Nowadays people prefer to click, but this catalogue remembers books that are no longer even in the index. Some... - he hesitated for a second - ...don't like to come out in PDF. Maks smiled crookedly, but Lena felt Mr Wisniewski's words catch somewhere in her imagination like Velcro on a jumper. - We're moving everything from 'Geography' to 'Habits'. If you come across something that doesn't fit, you put it back in the 'Unclassified' pile. And I'm off to get new boxes. 'Blob, don't sabotage! - he chuckled, but the cat just wagged its tail as if to say: I rule. They were left alone with the wardrobe, whose drawers whispered quietly with each slide. Lena gently pulled one out, smelling of old cardboard and ink. Cards written from the line with authors' names, titles, signatures. Maks turned one of the brass frames in his fingers, checking how it was attached. - 'Hey, look,' muttered Lena. - There's something strange here. Under the bottom row, in the shadows above the floor, was a drawer without a label. It slid in harder than the others, as if it hadn't been used for years. Lena and Maks looked at each other. The cat, Kleks, had eaten his whiskers but did not protest when Lena slipped her fingers under the handle and pulled. Inside lay cards unlike any other. Thicker, with sides frayed as if they were handmade paper. Instead of signatures, they had the words written on top in red ink: "IMPOSSIBLE RETURNS". - Is this... - Maks began. - Readers' cards? - finished Lena and lifted the first one. - 'A dictionary of travellers' dreams. Borrowed: 1974. date: when they return'. Who borrowed it? - She turned the card over. Instead of a name there was a drawing of an arrow and something like a plan. The drawer hid a dozen of them. On one ink was spilled in the shape of a wind rose, on another there was a name crossed out and written again, this time in some foreign alphabet. Lena reached for the last one and then felt her heart make a strange turn in her chest. The card was clean, only in the very middle there was a thin slit like a keyhole, and underneath there was a small, tiny inscription: 'Reading Room Times Sometimes'. On the back someone had drawn a short arrow and written: "Behind the sky atlases". The cat Kleks purred louder, as if he agreed. Maks brought his face closer to the card, then to the drawer. The ceiling light flicked on. - Behind the atlases? - he repeated. - 'I saw a rack of atlases by the windows today. Come on. Lena tucked the card into her sweatshirt pocket. They walked out of the warehouse into the main hall. The light became more milky. Above them, the clock still lurched at a minute eight past full. By the windows, the 'Maps and Atlases' section glittered. The backs of the books were painted with the outlines of the continents and the blue bands of the oceans. "Atlases of the sky" stood tall, right next to a stained-glass window with a polar star. - Who stacked it so high? - burbled Maks and climbed onto a stool with a librarian's measuring tape. - Pass the torch. Lena looked around. Under the catalogue table was a torch, heavy and cold. She handed it to her cousin. Maks shone it along the spines of the atlases until he came across a gap behind the books that could not be seen from below. There must have been more space between the wall and the bookcase than they thought. Maks picked up one of the atlases and moved it to the side. It creaked, but not like wood. More like metal rubbing against metal. The whole bookcase vibrated, then slid out literally the width of a hand. Behind it, in the shadows, something shone. - 'Oh dear,' Lena exhaled, climbing onto the stool next to it. - It's a ring. Behind the bookcase, a circle of matt metal was embedded in the floor, in a mosaic of dark stone. On its rim were embossed tiny numbers and symbols of directions. And in the very centre - a thin slit, exactly like the card from the drawer. The cat Kleks jumped onto the stool, then onto the bookcase, descended with his claws and sat down by the ring, as if waiting. Lena felt her fingers find the card in her pocket on their own. She took it out and looked at it again. For a moment, she had the strange sensation that the letters "Reading Times Sometimes" trembled, as if breathing. - You're thinking... - Maks began. - ...That it fits - finished Lena. - I think it does. They looked at each other. Nobody told them to. No one had forbidden it. And the rain outside the windows played like an orchestra about to play its loudest chord. At the top, the clock ticked and ticked and could not skip to nine minutes. - 'If it's some stupid device,' Maks muttered, 'then at most nothing will happen. And if it's not stupid... - 'This could be the most interesting Saturday of your life,' replied Lena and slid the card into the slot. For a second nothing happened. Then the air got heavier, like in a tunnel with a train coming up. The ring trembled. The clock above the door emitted a single, long 'tick', and all the cards on the desks rose and fell as if the library had sighed. Somewhere in the depths of the walls there was a rumbling, something clattered, the bookcases squeaked and shifted a fraction of a centimetre. From a gap in the ring, a flash of light passed onto the stone, onto the bookcase, onto their faces. The Cat Blob wagged its tail. At the edge of the ring, right next to the number 12, a tiny dot lit up. - 'Maybe we should take it out after all,' Maks said quietly, but he didn't sound like he really wanted to. The card surprised deeper, as if it had found its own way. Then an oval appeared in the heart of the mosaic - first just an uneven patch of transparency, then something like a sheet of water standing upright. There was no reflection of the brick in it, just the sky, where stars burned at midday. The air smelled of ozone, freshness and something like old blackboard chalk. - Can you hear it? - whispered Lena. There was a distant sound coming from that direction: a quiet clatter like from a counting machine, a whistle, the rustle of leaves. Or was it something to us? As if someone on the other side had pronounced a word we didn't know - and only understood that it meant: "Invitation". The cat Kleks didn't wait. With the grace of a black blob he leapt into the oval. A wave of coldness gushed over their faces. For a fraction of a second they could still see the tip of a white spot under his chin, then the cat's tail disappeared like a line of ink drawn inwards through capillaries. - Oh no. Blob! - whispered Lena, feeling her heart climb into her throat. - 'I don't think we're going to leave him there,' stated Maks, but there was something new trembling in his voice: excitement. - He needs to be summoned. Or... - 'Or go after him,' said Lena, looking at the taffy, which was now glowing with gentle pulses from within, to the rhythm of a very even ticking. - But not alone. Always together. They rested their hands on the cool metal of the ring. At the top, the clock, as if cut off from the rest of the world, stopped ticking and hovered at eight minutes. At the edge of the circle a succession of dots glowed, one after the other, like a countdown. At the third, something rustled in the magazine, as if someone was passing by, although no one was there. - Children? - came Mr Wisniewski's voice from behind. - Just two things: don't go in if the door is smooth, and... - he interrupted. - Actually, never mind. Excuse me! - And then his footsteps quickened, but instead of coming closer, they seemed to dissolve into silence. - 'I guess that means we're running out of time,' said Maks, 'see. The taffrail darkened and brightened as if it had blinked. A shadow appeared on its surface - the outline of something tall, which was definitely not a bookcase from this room. Maybe it was a column of plants, maybe a tower of books, maybe... something that held a yellow, broken chalk in its hand. Lena pulled her hood all the way down and swallowed her saliva. The cat was on that side. The dots on the ring were already jumping faster, and there was a growing hum in the air, as if someone was turning the world's volume knob. - Are you ready? - Maks asked. - 'Only in pairs,' replied Lena and squeezed his hand. They took a step forward. A chill bit into their fingers, like the first taste of ice cream in March. The taffy twitched, like the skin of a pond when a stone is thrown in. For a moment, everything became very quiet. And then, just before the tips of their shoes touched the passage, someone or something moved more distinctly on the other side - and looked directly at them.