A man with the mental capacity of a child accidentally saves an old man's grandson and receives a huge reward. Relying on his memory to search for his family, he finally returns home, but his other relatives, wary of the family property, are unwilling to recognize him and only want to drive him away. Only his older sister recognizes the birthmark on his body, firmly stands up to protect him, voluntarily gives up her share of the property, and guards her younger brother. Just as others try to snatch his money, the people secretly protecting him appear.