Once, an emperor had a pet nightingale. The nightingale sang the most beautiful and sweet songs that touched everyone’s heart. However, the nightingale was not happy living in a cage. One day, the nightingale lay in the cage and did not move. The emperor was very upset. Then a wise man came to see the nightingale. He opened the door of the cage and kept the nightingale on the windowsill. As sunlight fell on the nightingale, she opened her eyes and flew high up in the sky. The emperor understood that it was the cage that had made his nightingale sick. Five years later, enemies attacked the emperor’s kingdom. The nightingale heard the news and went to the battlefield. She sang such a melodious song that the enemy’s army fell asleep. Meanwhile, the emperor’s army captured the enemy soldiers. The emperor thanked the nightingale and she promised to visit him always.