During a heatwave in Kalisz, Marta and her brother are pulled into Igor's hunt for a hidden network beneath the city, and a stranger at the old cinema makes the whole thing feel dangerous.
It began in the middle of a July so hot the city looked exhausted. Kalisz lay still under a white sky, its centre nearly empty by noon, the pavements shimmering, the air thick enough to taste. Marta had never liked being stranded in the city for the holidays, but her parents were buried in work, so she and her younger brother, Adam, were staying with their aunt and trying not to count the days.
Boredom might have won, if Igor had not appeared.
Everyone in the district knew Igor. He was the kind of boy who always seemed to be following a clue no one else could see, with a notebook in one hand and a torch in the other, even when the sun was high. Marta found him that afternoon outside the abandoned Echo cinema, sitting on a cracked concrete planter as if he owned the place. He looked up with the sharp, pleased expression he always wore when he thought he had found something worth keeping secret.
"What are you doing here?" Marta asked, trying to sound unimpressed.
Igor grinned and tapped the side of his backpack. "Have you ever heard the stories about the tunnels under Kalisz?"
Adam gave a short, sceptical laugh. "The ones adults tell to scare little kids?"
"Maybe." Igor pulled out a folded sheet of yellowed paper and opened it between them. It was a map, old enough to be brittle at the creases, covered in thin winding lines, cramped notes, and symbols Marta could not make sense of. "I found it at the library. If it is real, it does not lead where people think it does."
Marta stared at the paper despite herself. Kalisz was old, older than most cities nearby, and everybody liked to talk about what might be buried underneath it. Ruins. Passages. Forgotten rooms. Most of it sounded like nonsense until someone held up a map with marks no modern hand would bother to fake.
"You want to go down there?" Adam asked.
"Tonight," Igor said. "If you're brave enough."
Marta was about to answer when a sound came from behind the cinema: the long, dry creak of the iron gate swinging open.
All three of them froze.
A figure stood in the gap where the shadow under the building was deepest. He was too far away to see properly, but not far enough to feel harmless. The lantern glass Igor had strapped to his bag caught a sliver of light and threw it across the stranger's face. His eyes reflected it back, bright and unreadable.
For a second Marta thought he was going to speak. Instead, he lifted one finger to his lips.
Silence.
Igor swallowed. When he spoke, his voice had dropped to a whisper. "We meet at midnight."
By the time Marta got home, the heat had turned the flat air inside the apartment into something heavy and restless. She kept thinking about the map, the dark mouth behind the cinema, and the man who had appeared exactly when he should not have been there. Adam kept pretending not to be nervous, which only made him look more nervous.
Neither of them slept.
At midnight, they were back outside the Echo cinema. The street was empty, the windows black, the old poster frames rattling faintly in the windless dark. Igor was already there.
So was the stranger.
He stood half in shadow, half in the thin spill of light from a broken lamp, as if he had been waiting for them the whole time. This time, he did not raise a finger to his lips.
He simply looked at Marta and said, "You should not have come."