Kuba never liked Mondays, but this one was completely different. As he crossed the gate of the Primary School No. 7, he noticed that the lights were on in the school attic, although no one was allowed in there. Kuba stopped for a moment, staring at the windows under the roof, where old, forgotten clocks had stood for years. Suddenly, he felt someone grab his arm. - Stop staring or we'll be late! - whispered Zosia, his best friend, pulling him towards the entrance. Right behind them trotted Wojtek, who always preferred to observe others rather than speak out loud. The lessons passed quickly, although Kuba could not stop thinking about the strange light. During the lunch break, he gathered his courage. - Did you see something going on in the attic? - he asked in a half-hearted voice. - Maybe it's the caretaker, Mr Marian? Or some kind of teachers' conference... - wondered Zosia, but her eyes were shining with curiosity. In the evening there was to be an astronomy show at school. Kuba, Zosia and Wojtek had signed up for it long ago. At 6 p.m. the whole group met in the chemistry room, where Mr Kosmala explained how to look through a telescope. After the show, the children were supposed to go home, but when Kuba, walking down the corridor, saw that the door to the attic stairs was not closed, he felt an irresistible temptation. - Come on! Let's see what's in there! - he whispered to his friends and before they knew it, the three of them were already tromping up the creaking stairs. Upstairs it was dark and smelled of dust. Suddenly, a loud sound came from inside one of the classrooms - as if a large clock had suddenly started striking twelve o'clock. But immediately afterwards there was a rustle, as if someone had stepped on the wooden floor and closed the door behind them. Zosia stopped with a pounding heart. - Did you hear that? Wojtek nodded, looking around in horror. Kuba twitched as a strange smell still reached his nose - as if of smoke or old paint. Then someone's hand slid out from behind one of the doors, and the window at the end of the corridor... opened by itself, letting in a shiver of cold air. The children stood motionless, not knowing what to do next. The stairs behind them suddenly creaked, as if someone else was going up.