The rainy afternoon was spilling grey light across the old house where Kacper and Lena were spending their holidays with their grandparents. Just when Lena was yawning widely and Kacper was unconvincingly trying to solve another crossword puzzle, Grandma appeared in the doorway with keys in hand. "Do you want to see something you haven't seen before?" she asked with a mysterious smile (or was it a smile? Maybe more like the shadow of a smile, which always heralded something unexpected). She led them to the cellar, whose door was always locked. They descended the creaking staircase, their eyes adjusting to the semi-darkness. The cellar smelled of dust, herbs and old books. In the middle of one of the walls, behind a row of crowded trunks, Lena spotted a huge mirror in an ornate frame whose ornamentation depicted swirling leaves. The mirror was slightly fogged up, but reflected the light in a somehow strangely doubled way, as if another world waited behind the sheet. Grandma looked at them with seriousness. "This mirror has been here much longer than all of us. No one knows where it came from. Apparently it doesn't just reflect what's in front of it..." Lena reached out her hand - touched the cool glass and.... in the same instant her fingers disappeared into the sheet. She freaked out and jumped up, but Kacper - always the more curious - carefully repeated the move. And he succeeded. They were emboldened by a strange, quiet whisper that resounded just outside their ears: "We are waiting for you..." Kacper looked at Lena and winked in agreement. They both placed their hands on the surface of the mirror. The glass rippled like the surface of a lake. Before they had time to think anything, they were pulled inside and their feet touched a whole new ground. They found themselves in a forest, but it was a forest unlike any other. The trees had white trunks, the leaves glittered silvery, and luminous orbs floated in the air. Lena thought she saw the shadow of a figure hidden behind one of the trees, but when Kacper turned his head, there was no one there. Everything smelled strangely familiar - like a house you visit in a dream. Suddenly, the forest lit up with a glow, and a figure in a long, dark blue coat emerged from the thicket. Its face remained in the shadow of its hood. The figure raised a hand, and their hearts began to beat faster. Was this a friend or someone they should fear? The figure raised its voice - quiet, melodious, like an echo in a cave: "Go deeper, if you dare." Kacper and Lena clasped hands. In front of them, the forest opened up to a path lit by soft lights, leading deep into an unknown world. On the other side, between the trees, something moved restlessly....