The abandoned theatre at the end of the street had fired the imagination of the locals for years, but only a few dared to cross its rusty gate. It was here, in the afternoon twilight, that Ola, Igor and Lena violated the rules of common sense - or maybe they were just looking for the adventure they had so far lacked during their monotonous days after school. The floor creaked under their steps as they made their way through corridors swamped with dust and cobwebs. Their torches cast pale light on faded posters and cracked theatre masks. "Can you imagine how much history there must have been here?" - whispered Lena, stopping by the ruined box. Igor, fascinated by all things mysterious, pointed to a door hidden behind a rolled-up curtain of gold brocade. "This is where I've never been," he chuckled and pushed open the creaking wood. Behind the door, in a small room, stood an unusual machine. It was built of brass and steel, full of clocks, levers, strange lights. Like a vehicle from a science-fiction novel. On the panel was an inscription engraved by hand: 'Time Curtain' and a barely visible sheet of instructions. "Great prop!" - Ola laughed, but as Igor touched one of the levers, the machine began to hum quietly. The clock moved the hands to the date of a hundred years ago. For a moment, the world swirled - the curtains returned to their place, the dust disappeared and the music of the old piano echoed from behind the wall. Through the doorway into the room came the voices of people dressed in costumes from another era. Lena looked apprehensively at the others: "This is no prop.... We really have moved!" At that moment, the door opened with a slam and a man with a stern look appeared in it, clearly not fitting the times they had just left. "What are you doing here?" - he asked in a voice that sent a shudder through them. The three friends held their breath, understanding that returning to their own time might not be as easy as it seemed....