“Don’t Buy the Seller,” a mystery thriller directed by Park Hee-gon, tells the story of Soo-hyun (Shin Hae-sun) who works at an interior design company and lives the ordinary life of an office-worker.

Soo-hyun struggles to deal with her workload and nagging boss and looks to online secondhand marketplaces for some income on the side.

One day, she buys a secondhand washing machine for 300,000 won ($224), but soon she figures out that she has been scammed. She immediately reports the fraud to the police, who are dealing with a number of similar cases. But, with no solid evidence, Soo-hyun gets on the wrong side of detective Joo (Kim Sung-kyun).

Soo-hyun’s character is bold and aggressive, so she decides to track down the culprit on her own. After finding posts online using similar phrases -- “I’m selling this because I’m moving abroad” -- she leaves comments to notify others that this post is fraudulent, warning people not to send money before receiving the item first.

After that night, Soo-hyun receives a number of strange phone calls and several food deliveries she did not order waiting in front of her door. At one point, someone tries to unlock her door and make entry into her house, saying that he had received a text message from Soo-hyun inviting him over for a one-night stand.

These strange occurrences are just the beginning for Soo-hyun, despite her efforts to change her phone number and install surveillance cameras in front of her home. Later, the police finally accompany her to the suspect’s home, but all they find there is a man’s dead body inside a refrigerator in the corner of an empty room.

This story of an ordinary woman targeted as the next victim of a murderer is not fictional.

Director Kim said the film is based on 2020 news and documentary programs that unraveled the case of a scam that further expanded into a murder case targeting secondhand marketplace app users.

“After hearing the news, I was shocked that this friendly, warm, community-based secondhand market was being used as a platform to commit heinous crimes, which traumatized victims and even led some to try take to their lives,” director Park told reporters after the film’s press screening on Monday.

“It was in the middle of shooting the film that we heard the criminal was finally arrested in Vietnam,” he added.

As the film is based on real life, the director wanted to focus on the real relationships between the police, victims and the criminal in a dry manner, rather than focusing on characters themselves.

Shin Hae-sun’s seamless acting also succeeds in immersing the audience and creating suspense. Shin’s talent is evident through the detailed emotional changes she skilfully portrays throughout the 101-minute film.

The characters around Soo-hyun, such as her colleague Dal-ja (Lee Joo-young) and detective Joo, as well as his assistant detective Na (Kang Tae-oh), make the storyline more realistic, artfully depicting their characters and making viewers feel like they exist somewhere out there in the world.

There are some scenes which follow the thriller genre’s typical formula, such as when Soo-hyun bumps into the criminal when she’s alone, or when detective Joo is unhelpful in the most pivotal moment. In spite of this, “Don’t Buy the Seller” is worth watching, because the criminal’s identity remains a mystery until the very end.

“Don’t Buy the Seller” opens in local theaters on Aug. 30.

If you’re thinking about self-harm or suicide, contact the Ministry of Health and Welfare’s helpline 1393, available 24 hours a day, 7 days a week. Please request a translator for English-language services.