Chow Tsz Yau
Last Friday, Mary brought a beautiful pen with bunnies and flowers on it to school. Everybody wanted to see this pen.
During recess time, Billy took away her pen secretly while Mary was playing at the playground. He wanted to bring it home.
Suddenly, Mary came back and found out her pen was stolen. Billy was very scared and dropped it behind the bookshelf in the corner of their classroom. The teacher asked those students who stayed in the classroom during recess time. All of them said they did not take the pen. Billy also said he had never seen the pen.
After school, Mary told Billy that the pen was her grandma’s gift. It was a valuable present before her grandma died. Billy felt very sorry and regretted what he did.
On the next day, the cleaner found the pen under the bookshelf. Mary was very happy that the pen was back.
Billy learnt a lesson. Since then, he has never stolen things and told lies.
In the end, still no one knew that Billy had stolen her pen, right? The sentence structures are clear and your ideas are shown very clearly.