The wife eventually discovers that the woman she suspected her husband was seeing was actually his sister, meaning he had remained loyal.
The plot involves the wife's sister attempting to seduce the husband to test his loyalty once more or force a mistake. Cast and Crew
The story of Season 1, Part 2 picks up immediately after the events of the first part, which introduced a young married couple whose happiness is threatened by outside influence:
Overwhelmed by guilt, the wife is further manipulated by her sister. Instead of coming clean, she is convinced to orchestrate a situation where her husband also "cheats," so they can both be on the same page of regret.