As the clocks in the Old Town struck midnight, no one noticed how a silvery mist flowed from the mysterious gate under the Town Hall. Sophie, Igor and Lena - three inseparable friends - were just then sneaking through the narrow streets, laughing quietly and checking if the legend of the underground passages was really true. The city's underground resembled a labyrinth: brick corridors branched off in all directions, and the echo of footsteps mixed here with the hiss of pipes and the rustling of rat's feet. Zosia stopped suddenly, leaning against a wall on which strange signs were carved. Lena turned on the torch on her phone - in its light the runes twinkled as if they were alive. Igor, bolder than usual, put his hand to one of them. Then he felt a slight tingling - first in his fingers, then all over his body. All three of them suppressed an exclamation of astonishment as they felt the world suddenly slow down and their thoughts take on an unprecedented sharpness. - 'What's going on? - whispered Lena. Zosia looked at her own hands. There were luminous patterns on their skin, just like the ones on the wall. She felt she could see through the brick wall, as if she had an X-ray in her eyes. Igor suddenly floated a few centimetres above the ground, as if gravity had ceased to exist for him. From around the corner of the corridor came a protracted, disturbing murmur - as if someone was watching someone. Lena, trying to calm herself down, thought for a moment that they were no longer ordinary children. Their powers were growing, and with them she felt watched. A silhouette emerged from the darkness, at which all the lights began to flicker. The friends froze motionless, ready to flee or... to fight if need be. No one knew who or what the figure in the shadows was - or what secrets the city's underground hid. Then a voice rang out, quiet but penetrating: - I have been waiting for you...