Darkness filled a corner of the old study. Lena touched the cool handle of a door she had never seen here before. The smell of old books and ashes mingled with something new - the light scent of mint. Dad always said you could find hidden nooks and crannies in old houses, but Lena didn't expect to find a whole door. One that shouldn't be here. Behind her stood Antek and Zośka. They could hardly refrain from questions, but the seriousness on Lena's face made them keep silent. Lena took a deep breath and pushed open the door. To the eyes of the three friends, a completely different world appeared - an emerald chamber illuminated by a light that seemed to flow from the air, with patterns of moving plants swirling on the walls. - Is this... a dream? - whispered Antek, approaching the wall, which suddenly swung open to reveal a passage further into the unknown world. The floor glistened, and quiet laughter and the sound of bells could be heard in the distance, although there was no one around. - 'It looks like someone is waiting for us,' muttered Zośka, bending down to pick up a silver key lying on the ground. The key was heavy, and as Zośka picked it up, the door behind them unexpectedly slammed shut with a bang. Suddenly the lights dimmed. Lena felt a cold shiver, and a shadow in the corner began to move. Was it just a breeze, or was someone actually hiding in there? Lena squeezed Annie's hand and watched as the shadow took on a human form. As the figure slid out into the middle of the chamber, Lena felt her heart pounding like crazy. Who - or what - was waiting for them on the other side?