KOREAN thriller Unlocked serves as a warning to anyone with a tendency to misplace their phone.

New to Netflix, the film is based on a novel by author Akira Teshigawara, and directed by first-time director Kim Tae-joon.

In a society where we are buried in our phones all day every day, it gives a chilling reminder of some real life cybersecurity issues and the dangers of putting too much trust in technology.

The film opens with a drowsy young woman, Na-mi (Woo-hee), getting off a late night bus without her phone after a night of partying.

The phone is found by Jun-yeong (Yim Si-wan), who comes across as a charming and mild-mannered loner — all smiles and a courteous demeanour. After making some modifications to the phone, he returns it, but, unbeknownst to Na-mi, he is watching her every move.

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With a serial killer on the loose, and the bodies of seven women discovered in a nearby forest, you can’t blame her doting father (Park Ho-san) for raising concerns about this strange young man, who infringes more and more on their daily lives.

Na-mi is overly trusting and starts to fall for this handsome stranger, who it appears can read her mind and seems to know her better than she knows herself.

More could have been made of the sub-plot about Jun-yeong’s father (Kim Hee-won), a detective charged with finding the serial killer responsible for the ghastly murders in the locality. Estranged from his son for seven years, he believes his offspring is not only capable of these killings, but quickly becomes the prime focus of his investigation.

Nobody makes thrillers like the Koreans, and while the plot, on paper, sounds fairly old and unappetising, director Tae-joon makes a fine feast out of his paltry ingredients.

It is far from perfect, and there are strands throughout the film that are flimsy. That said, it is entertaining and watchable, and will certainly leave you thinking about changing your phone settings.