Jagna lived in a trailer on the edge of the Biebrza National Park, just off the causeway. She spent her days in the reeds, setting up sound recorders and photo-traps for a research project. She knew the rhythms of the floodplain: the morning cries of cranes, the flights of geese, the nightly impatient splashing of otters. But this spring the animals began to move as if according to an alien, unsettling score. First she noticed a single path imprinted in the mud, strangely even as a line on paper. Elk hooves, tiny marten feet and heavy beaver heels were imprinted on the same line. Night recordings brought an even, pulsating tapping, recurring every two minutes like a metronome. No bird had ever tapped like that, no beaver had ever knocked on the water like that. - 'Maybe they're building something under the bridge,' muttered Staszek, the ranger, when she came to collect the battery supply. He was smiling with half his face, the other half busy with chewing gum and stories. - 'It's been too quiet under the Wooden Bridge for a week now; even the reedbucks have gone silent. - What about you? - She asked, tucking the notebook into her jacket pocket and pretending to be light-hearted. - 'I'm just shining a torch for you, lady biologist,' he replied, but handed her the thermos. At dusk, Jagna set the microphones on the railing of the Wooden Bridge and held her breath. The water seemed as flat as steel and a light, milky skin of mist lay above. A weasel emerged from the reeds, stopped beside her boot and stared into the black span. Behind her, a fox slid out, carried a blade of rush in its mouth, and laid it neatly beside the reed. Then something splashed and a slender otter climbed the beam, as if hurrying to meet it. Jagna activated the photopic viewer and scrolled through the night at an accelerated pace, staring. Side by side passed species that usually avoid each other stubbornly, like unwilling neighbours. Each animal carried a trinket: a stick, a sand shell, a piece of glass, thread from a bird's nest. They deposited it at the foot of the palisade, just above the water, patiently like workmen without words or tools. And then they all turned their heads to one side, as if listening to someone's feeble call. That evening the mist sat lower, and the clatter under the planks became clearer and more certain. Jagna stepped into the middle of the bridge, turned off her headlamp and slipped her hands into woollen gloves. A crane landed on her right, folding its wings so quietly that they rustled like grass. On the opposite bank stood a wolf, tall, wet, and not looking at the crane or the water. It was looking at it; and from under the pier, very close by, a quiet, rhythmic thump was answering. Something moved in the depths, as if it had unwound the night and was beginning to come out.