Sisters Must Be Happy

After marriage, Wang An becomes a neighbor to his wife Yifei's younger sister, Ruyan. Early one morning, summoned by Ruyan to fix a water pipe, he accidentally witnesses her brother-in-law Daqing meeting her privately. While intending to help, Wang An finds himself in a desperate situation. He must hide and seek help from his wife Yifei, but this very act pushes him into greater danger. Why does Yifei want to harm him? Can Daqing find him?