Maks has always loved the circus. Not the usual one, with elephants and cake-throwing clowns, but the circus where everything seems possible - even the impossible. When the red and white dome of Mr Barabas' Circus was set up in the town, Maks knew he had to go there, even if he had to enter through a small gap in the fence. And preferably with someone as curious as he was. Fortunately, there was Lena, his older sister. Lena could solve any maths task, but she liked puzzles and riddles best. Barabas Circus seemed full of puzzles right from the start. Already at the entrance, they were greeted by a spider bouncing on a boom like a spring and whispering, "Inside awaits what you won't find in any film!" Under the dome, it smelled of candyfloss and popcorn. Children ran around and artists flitted about in colourful costumes. In the arena, daredevils juggled flaming tentacles and flying trapeze artists cut through the air in the glare of spotlights. However, Maks and Lena liked the Cabinet of Mirrors best. The entry card said: "Warning! Here you may see more than you want to!" The walls reflected their faces in a thousand curved shapes. Maks laughed, seeing his own ears sticking up like hare's tails or Lena's nose suddenly reaching her chin. But after a moment, Lena pulled him by the sleeve: - 'See, there,' she whispered. At the end of the corridor of mirrors, the light flashed differently, as if someone had passed on the other side where there was supposed to be only a wall. They cautiously walked closer. Maks touched the glass sheet with his fingers. The mirror was cold, but he felt a slight tremor under his fingers, as if something on that side had responded by touching it. There were quiet whispers coming from behind the glass: "Come... see what waits behind the reflection...". Suddenly, the mirror shone with blue light, and a figure - a boy in a strange hat - smiled at them from the other side. He was not a reflection of either of them. - Is this an invitation? - whispered Lena. Maks nodded, sensing that any moment something was about to happen that he had not expected even in his wildest imaginings. Something completely unusual was about to begin in the office of circus mirrors....