Once upon a time, a Chinese emperor had a nightingale. It made him very happy day and night.
The nightingale can sing beautiful songs which kept the emperor in good health and spirit.
Another day, someone gave the emperor a mechanical bird as a present.
The emperor pressed the key and the bird would sing his song. This innovative toy thrilled the emperor so much that he forgot his nightingale. The nightingale left the palace.
One day the mechanical bird broke down. The emperor became ill and can not even get up, because his life had no songs to cheer him.
Ultimately the nightingale hoped the emperor could recover, so she returned. And The emperor recovered his health and spirit.