When Yu'er was 2 years old, her family changed drastically. She was adopted by her adoptive father Wu Xiaotian, who taught her medical skills. Before his death, her adoptive father told Yu'er not to forget her family's hatred. Later, Yu'er entered the house of drug dealer Du Yuanshan as a maid for revenge. When Yu'er achieved her goal, Du Yuanshan told her the truth of the year and gave her money to leave the Du family. Later, the Du family faced difficulties, and Yu'er was willing to return to the Du family to help them overcome the difficulties out of guilt. Du Minghai, the son of Du Yuanshan, had already had feelings for Yu'er. He believed that Yu'er sincerely helped the Du family, but the people in the Du family misunderstood Yu'er, but Du Yuanshan let her enter the Du family again. Yu'er demonstrated extraordinary medical skills and management skills and became the housekeeper of the Du family. Before his death, Du Yuanshan entrusted his family business to Yu'er. Yu'er also found her lost brother, the eldest master of the Du family, Du Mingjiang, but Du Mingjiang was blinded by desire and embarked on a road of no return. After the outbreak of the Anti-Japanese War, Yu'er stayed at the Du Mansion Pharmaceutical Factory and, with the help of the New Fourth Army, provided medicinal materials to the anti-Japanese forces and made good medicines for tens of millions of anti-Japanese fighters.