Dusk was slipping over the Bialowieza Forest as Lena sipped her summer tea in the wooden base. A GPS receiver blinked on the desk, each quiet ping marking one forest inhabitant she knew: the wolf Kora, the bison Plata, the scarred lynx that usually avoided paths. Lena liked the rhythm as if it were a lullaby of data, the hiking lines drawn on the screen, slow, persistent. The evening smelled of resin and smoke from the neighbours' campfire, and from the edge of the clearing came the subdued hooting of an owl, shorter than a step and insistent. Before she could close the laptop, there was a disconcerting rhythm on Kora's channel: short bursts and pauses, as if someone was dictating a cipher. On the map, she saw something stranger - Kora, Lobe and the two doe were following the same line, as if their paths had converged into a single track. Lena picked up the phone and dialled the forester's number. - Jan, can you see it? - I see it. And I don't like such convergences - he muttered. - 'Take the torch. Meet me at the bridge on the Hwoźna. The road to the bridge smelled of wet earth and aspen, the torch slicing the darkness into moving strips. A fox ran out of the thicket, disappeared and came back, eyeing them like a guide who hesitates to trust tourists. Above the water, the woodpecker fell silent and the usually noisy starlings moved higher up, as if they preferred a clear view of the ground. - Have you got it? - Jan pointed to the receiver. - They all go to the Old Chrusty. - There's nothing there,' she replied. - That's why it worries me. The clearing at Stare Chrusty looked like an amphitheatre without spectators, although the spectators were already there. Bison were standing in a semi-circle, doe were motionless with their ears set like antennae, and the shadow of two wolves could be seen at the edge of a pine grove. They were not growling. They were waiting. In the middle stood the withered trunk of an oak tree, darkened by storms and years. The receiver murmured a new signal that Lena didn't know: the device called it "unidentified". - Who would have a transmitter here? - whispered Jan. - 'No one sensible,' she replied, feeling her curiosity grow. A fox, the same one who had led them away from the river, ran silently up and placed a gnarled, muddy strap beside Lena's shoes. She shuddered as she recognised the number stamped into the metal: 07. The collar of a lynx whose signal had gone silent last year. - It can't be," she whispered. A barely perceptible sound flowed from within the trunk, low as the purring of the wind beneath the threshold. The ground responded with a twitch, and the bison simultaneously took a step back. - 'Don't move,' said Jan, raising his hand. At the same moment, all the collars beeped in one long tone, and something in the darkness moved towards Lena.