Astrid Larkson is a 19 years-old girl who's studying to become a psychologist. She's in her first year of college, majoring in Psychology and minoring in Forensic Science. Astrid is your typical shy girl, choosing to huddle up inside watching movies than meeting up with friends on a night downtown. She got an internship recently and now, she must accompany Park Chanyeol, a professional psychologist working for the LA police department, to a murder scene. A new movie called "The Way We Were" chooses LA to be the site of the first few scenes. However, the male lead gets killed in his hotel room. Mr. Park's job is to provide comfort for the mourning staffs and to question them abou the murder. One day, Mr. Park calls in sick, leaving Astrid to attend the meetings herself. She meets Sehun, a supporting male actor, who seem to have very toubling background. Could he be the culprit? Astrid finds herself falling for him, even though she knows he's not good for her. Find out how the mystery unravels in "The Reason Why."