The evening on the Silver River flowed like cold ink that someone had smeared with a paintbrush over the bank, reeds and wet stones. The old ferry, long since defunct, stood moored to the decayed pier and creaked with each gentle ripple. Overhead, the yellow light of the harbour lamp stung the darkness like the only eye, and beyond - silence. That, at least, is how it should be. On this day, the silence was full of whispers. Nina leaned over her phone and swiped her finger across the map. The flashing dots, each a different colour, merged on the screen into one dense blur. The labels spoke for themselves: Simon - the hedgehog from Railway Park. Runa - a fox from the allotments. Dot - an otter that took a liking to the sluice. Dot - a cat that slept half the day on the windowsill of the library and wandered half the day on the quay. And the white triangle signifying the stork, whom the pupils named Zenon because he always returned to the same post. - They really are here,' she muttered, biting her lip. - Not nearby. Here. In one place. Bartek leaned his shoulder against the railing of the bridge, looked at the screen and whistled quietly, but was soon silent as the flock of gooseflies circling over the water rose restlessly. - This makes no sense. A hedgehog, a stork, an otter, a cat... Each from a different fairy tale, and suddenly they're all picking the same dot on the map? - He scratched the back of his neck. - Either the app has gone crazy, or.... - Or there's something going on that we don't understand,' Nina finished. Her fingers automatically touched the slight scar just above her wrist - a reminder of her first, too daring attempt to feed a terrified swan as part of her volunteer work at the Paw and Feather clinic. Since then, she felt like she was learning a different alphabet: the meaning of footprints in the mud, the warning hiss, the way the wind carries scents over the water. - Ms Rogowska said that when something looks like a joke, you have to check whose joke it is. 'Urban Animal Atlas' was their project for the school's science festival. The GPS transmitters they strapped to a dozen animals under the guidance of a veterinarian and the city were intended to help them understand how they create their own routes through tight streets, gardens and parks. Throughout the spring, the data formed sensible stories: circles of territories, repetitions of returns, nocturnal wanderings. And then, today, the graphs suddenly began to converge like rays to a single point - the old ferry. Three crows flew out of the darkened cove, circled wide and sat on the winch. They sat so evenly that Nina felt a slight shudder. Bartek pulled a small sound recorder and lightweight, puffy microphones - borrowed from the film club - out of his rucksack. - You say they 'go like clockwork'. Maybe we can hear something we can't hear," he said in almost a whisper. They made their way lower, between the twisted railings, where the shade smelled of metal and rusty water. The reeds rustled as if someone had moved their hand over the silk. Nina switched on the recorder and watched the histogram: the green dashes vibrated in a rhythm so quiet she could barely feel it under her skin, in her cheekbones. It wasn't the usual hum of a lamp, or the distant roar of a motorbike. Something deep vibrated here, as if the river hummed a single, low note. - See? - Bartek pointed to two narrow peaks on the display. - Ultrasound. Almost at the limit of what our microphones catch. That would explain why people didn't notice anything. - But why? - asked Nina, not expecting an answer. - And who? A thin shape emerged from the mist above the water table. An otter. It stopped at a floating log, emerged with its muzzle and, stranger than its mere appearance, looked exactly in the direction of the ferry. Then, as if on signal, the deer moved - two, maybe three - bouncing off the wet banks until they stood in the dense rushes, where they disappeared almost entirely. A hedgehog, swollen with autumn grease, rolled slowly down a stone alley from the park. And from the gloom on the left a fox flashed by, low to the ground, tail low but without panic. Neither of them paid any attention to the humans. It was as if Nina and Bartek had stopped belonging to the world of important things for a moment. - 'I'm filming,' whispered Bartek, picking up his phone. - 'Don't turn on the torch. I don't want to scare them. Nina nodded her head. Instead of the light, she opened the notes on the app: 9:37 p.m. First animals at the ferry. A small crowd in the reeds. An audible sound - low, continuous. Birds perched on the railing of the ferry. Zero human movement. The latter was untrue when you think of the crows. They sat still, like black pins plugged into steel. And at the same time Zenon, the stork who had been training for weeks to fly away, flew in from the south and, as if unwillingly, tightened his circle. He then descended low over the river, slid past the ferry and landed on the other side, just opposite. Birds don't just land anywhere when there's nothing around - even Nina, who still felt more like a student than a researcher, knew that. Bartek brushed her shoulder with his elbow. - That's not all. Look - he said, scrolling through the map. - The transmitters... On the screen, the different coloured dots - one after the other - stopped and faded away, as if someone had put their finger on the buttons and muted the living instruments one by one. They did not disappear. They simply stopped sending a new position, as if they were waiting for a command. Somewhere further away, beyond the light of the lamp, something banged against the metal. A dry click, silent but so unexpected that the sound climbed up Nina's throat. - What's that? - it slipped out of her. - 'Maybe the rope has come loose,' replied Bartek, but he didn't sound convinced. They moved so that they were shielded by a lighting pole. The ferry didn't look dead: it had water, rust and time in its veins. But now Nina saw something else - three crates, tied with straps to the central deck. They were new, made of smooth, dark plastic, with small vents on the sides. They were almost invisible from behind the railings, but Nina flashed a shiny shape inside - as if something had moved. The thought that popped into her head was so simple that she didn't want to let it go: someone could be transporting animals. Illegally. Across their river. - Can you smell it? - Bartek wrinkled his nose. - Like... citrus. And grease. - The smell was pungent, alien to this bit of shoreline, where usually only mud, fish and barbecue smoke floated. Nina touched the edge of the railing. A smudge of oil soaked with something remained under her fingers. - If it's someone else's... - she started and broke off. Because it was someone else's, no question about it. But whose and why - she didn't dare name it out loud. The recorder trembled in her hands: the bands on the screen narrowed and flickered. A sound that had hitherto been background, like the purr of a distant refrigerator, suddenly broke in until the air became heavy, as if rain hung in it, though the sky was clear. The frogs in the reeds grew quiet. The birds on the winch moved restlessly and then - all at once - turned their heads in the same direction. - 'It's a signal,' said Bartek with his eyebrows drawn together. - Someone is turning it on on command. - But where is the transmitter? - Nina asked. She looked around, clinging to the shadows. She was sure that if they shone the torch, everyone - them, the animals and whoever was pushing the buttons - would see each other all too clearly. Then they heard a growl. Not loud, not like a speedboat engine. Higher, more even, with a quiet, slightly sour hum. Above the ferry, at about mast height, hovered something the size of a large seagull, with four propellers, red dots instead of eyes and a camera that rotated lazily, like a lizard's eye. - 'Drone,' breathed out Bartek. - Don't turn the phone on! - he added immediately, as if he only now realised that every flash was a betrayal of his position. The drone approached the crates and stopped in place, modulating its tone. Nina saw dozens of tiny dots light up amber in the rush - eyes. Single, double, low, high. They did not blink. The whole assemblage of living creatures stared at the ferry as if waiting for a password. The phone in Nina's pocket vibrated. She tried to silence it, but it was too late: a short, deep "bzz" cut the darkness. The drone lifted a few centimetres and its camera ran over the shore like a cold finger. They crouched reflexively. The ground under their boots was cold and damp. Nina felt the saltiness of the river on her tongue and the metallic aftertaste of adrenaline fear. - 'Someone's controlling this,' she said, until her teeth clattered lightly against each other. - 'It's not a coincidence. They... A rustle behind her cut her in mid-sentence. Not in the reeds, not by the water. Just behind them, on the path where fallen branches formed an arch. Someone or something had stepped into a dry leaf so close it couldn't have been the wind. Bartek froze. He turned his head millimetre by millimetre. Nina heard the fabric of his sweatshirt sliding across the grass. Two dots shone in the darkness between the willows. For a split second they could have been anything: the reflection of a lamp in a piece of glass, a night-time worm on a leaf, two ordinary dewdrops. It was only when they shifted a hair's breadth that she realised they were looking. At them. On the ferry, meanwhile, the drone began to lower its flight, and one of the crates moved more violently, as if something from inside was pushing against the wall. All the lights - the lamps, the LEDs, the amber flecks in the reeds - seemed suddenly sharper, like stretched strings. - 'Nina,' whispered Bartek so quietly that she hardly felt the air move. - 'Don't move. Something heavy took another step. And another. The drone whined higher, the ferry creaked and the water at the side swelled with an unreal wave, as if something huge had moved beneath the surface. As a stream of cold, white light cut over their heads, and a warm, moist breath reached Nina very close to her neck, she realised that they were no longer just observers.