Zosia didn't like Mondays, but this one was special. The wind had been howling outside the window all night, so she came to school in the morning with a head full of strange dreams. As soon as she crossed the threshold of the old building, she saw her two friends, Paul and Klara, sitting under the stairs and whispering something mysteriously. - You have to see what we found! - whispered Klara, pulling her by the sleeve. Paul was as pale as a sheet of paper and all the time he was holding some strange, shiny key in his pocket. Wiping her dusty glasses, Zosia ran with them to the cellar, the entrance to which was obstructed by an old broom. On the wall, right next to the heating pipes, there was a door smoothly blended in, which they had never seen here before. Paul took out a key and, with a trembling hand, slid it into the lock. When the door opened, they saw a small, circular room. In the middle stood an old table, on which lay three paper masks. Each was signed with a different name: Zosia, Paul, Klara. - Is this... for us? - Zosia asked, looking at her friends. Suddenly the light on the ceiling came on and letters appeared on the wall: "SELECTED. YOU HAVE 7 DAYS TO DISCOVER YOUR POWER." Zosia felt her heart start to beat faster. Do they really have superpowers? What would happen if they didn't make it in seven days? The door slammed quietly behind them....