It all started on a grey, rainy Thursday when Simon, Lena and Kuba stayed after school in the town's library to complete a history project. The library, built back in the 19th century, was a place full of creaking floors, the smell of old volumes and legends that the town's elders liked to tell at dusk. As the clock struck seven o'clock, Lena rose from the table and stretched lazily. "Let's finish up before Mr Zaleski kicks us out," she muttered, packing her books into her backpack. Cuba looked out of the window at the puddles spilling over the pavement. "I don't want to walk in this rain," he sighed. Simon, however, instead of gathering his things, stared at an old map of the city they had found by chance in one of the volumes. Something intrigued him. "Look at this," he said, pointing to the indistinct lines under the library. "It looks like some kind of corridor or chamber." Lena took this as further evidence of Simon's obsession with mysteries and old buildings, but curiosity won out. Moments later, the three of them were already following Simon, who was leading them down a spiral staircase into a rarely used underground. It was dark, damp and dense with silence. Cuba fired up the torch on his phone. After a while, they came to an old iron grating, behind which a corridor was dimly visible. To their amazement, the lock on the door gave way easily and the door creaked open wide. In front of them stretched a narrow tunnel carved in stone. The walls bore mysterious symbols and inscriptions, the meaning of which they could not decipher. After a dozen metres or so, the corridor ended in a small, oval chamber, in which a piercing chill prevailed, although the air was still. In the middle of the room was something that resembled a huge mirror, framed in tarnished silver, with a surface that reflected nothing but deep darkness. Simon took a step forward. "It must be... a portal," he whispered, fascinated. Lena glanced nervously at her phone - no reception. Cuba cautiously touched the frame of the mirror; he felt something attract his hand, although by sheer force of will he withdrew it. At that moment, a strange, quiet laughter came from the darkness of the mirror. The chamber began to vibrate gently, and the symbols on the walls flashed with a pale blue light. Suddenly the air swirled, enveloping them in a chill and drawing them closer and closer to the surface of the portal. Lena screamed, trying to grab Cuba's hand, but they had long since lost track of where reality ended and something else entirely began. Everything around them turned into a swirling darkness, and the echo of old voices pierced through the swish of the air....