The Old Town Library smelled of dust, paper and something intangible that made the hair on the back of your neck stand up sometimes. None of the adults looked there anymore - except for Mrs Zosia, the librarian, who claimed that "books need silence and holy peace". But Maja, Patryk and Lena loved the library mazes. Every Friday, right after school, they would sneak off to the farthest bookcases, where the shelves were heaving with volumes unread for years. One afternoon, Lena noticed a light flickering strangely behind the encyclopaedia bookcase. - Look! - she whispered and pointed to a narrow gap behind one of the bookcases. The friends squeezed through the pile of books and stood in front of a door they had never seen here. It was old, wooden, with a mysterious spiral carved in the middle. A small key hung on the handle. - I don't think we should... - Patrick started, but Lena was already turning the key in the lock. The door opened with a quiet creak. Instead of a dark warehouse, on the other side stretched a luminous tunnel in which coloured sparkles floated. Distant laughter, the sound of bells and something that resembled the rustling of wings could be heard. - Shall we go? - asked Maja, squeezing her friends' hands tightly. They took the first step and felt the air around them tremble and the world spinning faster and faster. At one point they fell into complete silence and.... they found themselves in an illuminated clearing, where trees grew with leaves like coloured glass. In the middle of the clearing stood something that looked like a huge, rune-covered portal gate - and around it loomed strange creatures with feelers and butterfly-like wings. Suddenly, one of the creatures flew up to them and whispered: - We have been waiting for you, Guardians of the Portal. You have very little time. The friends looked at each other with wide-open eyes. What would happen now?