Lena combed the map of the town with her eyes. Her finger stopped on a small dot, next to which someone had haphazardly written - "old tower". Apparently it was invisible to adults, which meant that no one outside the children's pack believed in it. But Lena knew her own. She was fifteen, curious and dared to look for answers where others didn't even ask. That day, she and Maja climbed through overgrown gardens and twisted paths until they saw it hidden among the mist and mossy trees. The tower seemed taller than anything else in the area, and its stones shone with an emerald glow, as if someone had sewn particles of light into them. - 'Hey, can you see that? - Lena asked, pointing to a door that appeared suddenly, sliding silently into the wall. Maja nodded, falling silent in surprise. After a few minutes of hesitation, they slipped inside. The tower was cool and slightly damp, the air smelling of old books and something elusively sticky. Skylights swirled on the walls, arranging themselves in strange patterns. Whispered words floated up the stairs leading upwards - Lena didn't know if she really understood them or if she just thought she did. At the top they found a circular room, in the centre of which stood a huge mirror, framed in a black wood frame. The frame was touched by silver veins; sometimes they glittered like lightning. Shadows flitted across the surface of the mirror. Before Lena had time to ask Maja if she was seeing the same thing, one of her hands unconsciously brushed the surface of the mirror. The room was illuminated by a green light, and a voice - at once familiar and completely unfamiliar - came from inside: - Do you dare to cross to the other side? The girls looked at each other with wide-open eyes. They felt that this was the moment after which nothing would be the same as before....