Shen Mingzhu, a female doctor who studied abroad, returned to war-torn Shanghai with her five-year-old cute baby Shen Xiaobao. She wanted to live a low-key life practicing medicine, but she was involved in the whirlpool of a spy war between the underground party and Japanese spies. Her fiancé, Lu Ziqian, came back from the dead but became the object of double suspicion from the military commander and the underground party. Her former best friend Zhao Xuelan became the spy chief and pressed her every step of the way. Shen Mingzhu relied on his medical skills to gain a foothold in the concession, but discovered that her five-year-old son was actually a genius and could remember all the enemy's secret codes and passwords with a photograph. Xiaobao became the most unexpected secret weapon, and mother and son joined forces to dance on the tip of the knife. Lu Ziqian wanted to protect them, but every time he got close, it would bring greater danger. Zhao Xuelan retaliates wildly, the military commander wants to take advantage of them, and Zhou Zhenbang, the eldest brother of the Youth Gang, fights to protect her. Shen Mingzhu was forced to choose between the benevolence of a doctor, the affection between mother and child, and the justice of the family and country, and Xiaobao's talent became the target of competition from all parties. A sadomasochistic love affair about protection and sacrifice kicked off amidst gunfire.
