In an apartment, two sisters live upstairs and downstairs. The elder sister Ruxing (played by Zhu Zhiying) is a writer, and the younger sister Ruyi (played by Zhang Junning) is a photographer. They are busy with their careers all day long and their lives are uneventful. One day, Ruyi accidentally captured a picture of a man and a woman having a happy time. Later, she found out that the woman was having an affair behind her husband's back, which made her curious, so she deliberately explored the woman's life. Ruyi told her sister about this experience, which also aroused Ruxing's interest. Ruxing encountered a creative bottleneck, so she decided to write this affair into a novel. But Ruyi accidentally discovered that the plot in her sister's novel seemed to reflect the experience of the man and woman in the next few days. She realized that her sister was hiding something from her, and the sisters inevitably began to affect the lives of the strangers...