In the early years of the Republic, Lin Xingran, a medical student who studied abroad, returned home to find her mother brutally murdered. To uncover the truth and seek revenge, she infiltrated the home of the prime suspect, the wealthy Mr. Fang, under the guise of a family doctor. Unexpectedly, Mr. Fang was murdered, and Lin Xingran became the prime suspect. To make matters worse, the investigator was Mr. Fang's adopted son, Jiang Beichen, who was also Lin Xingran's former lover. He believed that two years ago, Lin Xingran had betrayed him for wealth and status, and he was determined to settle old scores along with new grievances. The two engaged in a battle of wits and strategy, sparking an intense cat-and-mouse game filled with narrow escapes. After discovering that the true murderer was someone else, they collaborated and rekindled their old romance. However, at that moment, Lin Xingran realized that Jiang Beichen might very well be the one who killed her mother, turning their identities upside down.