At a certain colourful school, in class 1B, the children had just finished drawing beautiful pictures. Tosia had drawn her favourite owls and Kacper a big green dinosaur. Suddenly Tosia called out: - Where are my blue crayons? They were just here! Kacper looked in his pencil case and was also worried: - My red crayon is missing too! The children looked around the classroom, but the crayons were nowhere to be found. Mrs Anna came to help them, but even under the desks she could not find anything. Tosia looked at the windowsill and saw a strange shadow there... Was it a mouse? Or maybe something else? As they all came closer, they suddenly heard soft giggling from behind the cupboard door....