Maja enjoyed going to school very much. Her classroom was colourful, there were drawings on the walls and green flowers under the window. One morning, when the children entered the classroom, they noticed something strange. On the blackboard someone had drawn a large, spiral line with white chalk. The beginning of the spiral led all the way to the floor, between the desks! - Who had done this? - asked Mrs Iwona, and the children just rubbed their eyes in surprise. Nobody admitted to the mysterious drawing. They all gathered around the spiral. Franek squatted down and touched it with his finger. - Look! - he called out. - This trail leads all the way behind the bookcase! The whole class started walking silently along the chalk trail, trying not to smudge the white line. They looked under the teacher's desk, behind the dustbin, until suddenly.... Behind the bookcase, the trace disappeared. But were they sure? Maja noticed something lightly glowing behind one of the pictures. Everyone froze in surprise and looked after each other with big eyes. Should they look behind the picture? Or is that where the big school secret is waiting for them?