The wedding is perfect until the bride receives a letter claiming the groom spent the previous night with someone else. This marriage is crucial for both families' financial interests, and various personal and professional stakes are tied to it. The groom's friend grows suspicious, and the bride, a teacher on the verge of a promotion, faces immense pressure as her reputation and career are on the line. As tensions rise, the groom confesses he was unfaithful, and the bride faces a tough decision that could shatter her life.
Chinese secret agent Da-hee receives intel that a large number of illegal firearms are being smuggled into Korea and is sent to investigate the case. She meets Su-han, who is supposed to help her with the case, but due to his lackluster skills they fight over trivial things. But as their witnesses are suddenly murdered, the two of them quickly become the prime suspects.