The film follows (Konstantin Beloshapka) and his fiancée Katya (Vera Kincheva), a young couple whose path to marriage is derailed by a seven-year-old social media post. As a teenager, Sasha shared a photo of his then-girlfriend, Masha, to impress his friends. Years later, even though he has moved on, the internet—and a vengeful spirit—have not.

It tackles the darker side of how social networks and instant messaging influence modern relationships.

Reviewers have highlighted several elements that make La Ex a noteworthy addition to the horror genre: