Warsaw 2096 smelled of ozone after the storm, and the glass embankments by the Vistula River glimmered with advertisements. Seventeen-year-old Lila Maj, an intern at the city's data lab, was browsing through streams of sensors. For the 'Discover the Hidden' competition, she was missing something that didn't fit in the instructions. She found bite-sized two-second holes in the graphs from the river bottom, repeating every hour at Czerniakowski Port. The holes didn't have an error, they had a pattern. She downloaded the raw sonar logs and ran them through her own filter. A heart-like rhythm appeared between the noise, written in intervals of prime numbers. In the middle of the compressed block waited a cryptographic signature with an address: "Lila May". The time stamp read 2084, long before her first account was created. She opened the contents in the sandbox. There was only one sentence: 'Come at 23:40, knock three times, take Oscar'. Oskar was waiting for her on the platform, between the aerotramway stop and the milky algae hall. "If it's a prank, you'll buy me cocoa for a week," he muttered, but his eyes were shining. They rode the service lift down under the glass shaft, using Lila's school pass. It smelled of cold, metal and old paint, and the air carried the quiet murmur of the river overhead. They walked along the cable troughs, passing cleaning robots like small, lurking dogs. Lila jammed their transmitters with her bracelet, feeling the tension grip her neck. At the end of the corridor, a steel door with a faded sign waited: ARKA-W2. An old panel displayed a countdown that would reset at exactly 23:40, two minutes from now. Then the screen flicked on and wrote her name, in letters like from a teacher's diary. Lila knocked three times. The service lights dimmed and the noise overhead grew deeper. The panel gave off three short tones, like an echo of that rhythm from the logs. The bracelet vibrated at the rate of an alien pulse, at odds with her own heart. Their displays showed notifications from "Lila Maj" transmitted simultaneously from two locations. "I'm not sending anything." - she whispered, taking half a step back. A valve hissed from the other side of the door and the circular peepholes parted like eyelids. Lila saw the same corridor on the other side and two silhouettes in identical jackets. They, too, were looking, but they moved a fraction of a second later, like a recording with a slight delay. Somewhere behind her back something clattered against the grating, a single, sure step. Oskar raised his hand, asking for silence, but the sound was repeated closer.