The average person spends a third of their life asleep. It’s no wonder that some feel the need to use some of that valuable time to be more productive, by talking in their sleep, or even sleepwalking. And who knows, maybe those that talk in their sleep make more sense when they do.

This South Korean film follows a couple about to have their first child, when the husband starts to get more active in his sleep.

During the day Hyun-su (Lee Sun-kyun) is an actor. His pregnant wife Soo-jin (Jung Yu-mi) notices that he has started to develop another role for himself during sleep, that of talking. Although he says a few things that are a little alarming, she isn’t overly concerned.

That changes when he starts sleep walking, even getting to the point where he puts himself in danger.

It gets so bad that they decide to seek medical guidance for it, and see a sleep specialist. He is confident that Hyun-su has nothing to worry about, and he just needs to change his lifestyle somewhat, as well as take some medication.

He is happy to do all this, for a quiet night’s sleep, which is a relief for his anxious pregnant wife.

The situation doesn’t get any better though, and after their baby is born, only causes Soo-jin to stress out even more.

But after discussions with her mother, she puts in her mind that maybe it isn’t a clinical sleep issue after all, and perhaps something far darker at play.

Jason Yu’s directorial debut, which he also penned, is a confident start to his fledgling career. The South Korean director, who previously assisted on Bong Joon-ho’s 2017’s Okja, has made a bold and vivid film about a family coming to terms with a sleep disorder.

Initially it’s fairly playful, with the leads proving to be an engaging on screen couple, who face a serious issue in their lives.

Then Yu decides to turn a darker corner, with the film taking on more of a horror tone for the latter half of the film. It’s an interesting gear change, that shouldn’t really work, but Yu makes sure that it does, having done some good work in getting his audience to invest in his young couple. He then creates a more tangible, undercurrent of the afterlife to proceedings, which works surprisingly well.

Sleep then is an imposing debut, that handles fairly generic material by cranking up the atmosphere and thanks to Yu, gives it a welcome wake-up call.