Dusk had long since fallen over the city when the lights and sounds of the Red Circus exploded in Green Bridge Square. Three people - Lena, her brother Kuba and their friend Irek - stood in front of the entrance, gazing at the huge, shimmering dome stretched over the tent. Glittering flags fluttered in the wind, inviting them into a world of shadows, light and things that cannot be easily explained. Lena had been talking about this one night for weeks now. She had always been curious, and ever since rumours of strange disappearances and mysterious performances at the circus had been circulating on the internet, her curiosity had even turned into an obsession. Kuba tried to stop her, but Irek was always on the adventurous side. So there they stood, tickets already tucked in their pockets, with hearts pounding. Inside the tent, the smell of candyfloss, popcorn and cinnamon apples mingled with the excitement of hundreds of spectators. A trapeze artist twirled in the air, a magician caught the crowd's gaze and clowns performed their bizarre jumps. Yet everything seemed more beautiful and unusual than in any circus they knew. During a break, Lena noticed how, under a not particularly conspicuous curtain, two artists in black tailcoats were moving a huge box. The box was decorated with the symbol of an eye inscribed in a triangle. They whispered something amongst themselves, glancing back at the audience time and again. Lena pulled Kuba and Irek by their sleeves. - 'Look over there, backstage. Someone is hiding something in that strange box! - she whispered. From the looks of it, it was heavy and solid. Irek, heedless of anyone, slid closer, but suddenly one of the artists raised his head and looked straight in their direction. The boy immediately hid behind a pillar. After a moment, the box disappeared behind the curtain leading to the forbidden part of the tent. During the next show, as the lights dimmed, Lena felt a sudden tingling in the back of her neck. Right next to them, among the happy audience, a strange man with a lass and a cylinder was strolling by, but only she seemed to notice him. He was whispering something to himself, as if he was warning someone. Kuba and Irek also noticed him, and his gaze stopped on the three of them. As the show came to an end, the crowd slowly left the circus rows, but Lena could not move. She had the feeling that the circus wouldn't let them leave until they solved its mystery. Suddenly, the lights dimmed completely and one of the clowns ran out from behind the curtain. Instead of a smile on his face, he had an expression of panic and threw something in their direction - a key with the symbol of an eye inscribed in a triangle. - Put it away and don't trust anyone! - he hissed, before disappearing into the crowd. Holding the mysterious key, Lena, Kuba and Irek felt that they had become part of something that went far beyond a mere circus performance. In front of them stood a curtain leading deep into the forbidden part of the tent. Their decision could change everything...