Channel A's 'Detectives' Trade Secret' will cover the concerns of a woman who is six months into her marriage. After being summoned by her mother-in-law and visiting her in-laws' home, the client found herself in a situation where her brother-in-law seemed to be making romantic advances toward her, prompting her to entrust the investigation to the detective team. As the case unfolds, the hidden incidents behind it are revealed one by one.

The brother-in-law told the client, "Sister-in-law, you look so pretty in your uniform. I think it would feel really nice to receive service from you." He also deliberately dropped objects and then peeped at the client from under the table.

At a family gathering at the couple's newlywed home to celebrate her husband's birthday, the brother-in-law was spotted coming out of the master bedroom carrying a suspicious bag. He explained, "I left a gift for my brother as a surprise," and indeed, a present for the husband was sitting in the room. However, the next day, the client discovered that her uniform had gone missing, and suspecting that the brother-in-law had taken it, she requested an investigation by the detective team.

According to the detective team's investigation, the brother-in-law had been living without any particular job, managing a building owned by his mother. People around him described him as "really good to his mother" and "the most filial son in the world." However, when an unexpected secret was uncovered as the detectives traced his whereabouts, the cast members could not hide their shock. Defconn reacted, "Is this even possible?"

On this episode, Park Jung-ah, the leader of the group Jewelry, appeared as a one-day detective. Park Jung-ah, who has been married for 11 years, said she relieves her anger by knitting after fights with her husband. When Defconn asked whether she knits even while watching the show, Park Jung-ah said, "It just keeps boiling up," and showed off her dishcloth collection, livening up the atmosphere on set. When Kim Poong asked, "Just how many things have made you angry all this time?" Park Jung-ah replied, "There are more at home."

Meanwhile, 'Detectives' Trade Secret' airs on Monday, August 17 at 10 p.m.