Based on the novel In This Way I was Saved by Brian DeLeeuw, Adam Egypt Mortimer directs and co-writes Daniel Isn’t Real, a psychological horror starring Miles Robbins, Patrick Schwarzenegger and Sasha Lane and which had its premiere at South by Southwest earlier last year.

After witnessing the aftermath of a mass shooting, Luke (played as a child by Griffin Robert Faulkner) meets Daniel, a friend no-one but him can see. The two grow close, lost in an imaginary world of fantasy and heroism, until the day Daniel tricks Luke into killing his mentally ill mother (Mary Stuart Masterson) by overdose. She survives and, learning what has happened, forces Luke to lock his imaginary friend away in a dollhouse.

Courtesy of Arrow Films

Flash forward to twelve years later and Luke (Miles) is now a depressive, insecure law student with a mother whose state of mind is growing increasingly worse. After a particularly bad episode, he is forced to commit his mother to an institution, the emotional toll of which leads him to bring back Daniel (now played by Schwarzenegger) as a way to cope.

Though the film’s first act is well-worn horror movie territory, adult Daniel’s introduction gives the narrative the energy it needs to keep the audience invested. Under Daniel’s guidance, Luke grows more assertive and sociable, quitting law, flirting with girls and getting close to cool-girl artist Cassie (Sasha Lane). At first a charismatic, sleek Ferris Bueller type, Daniel slowly transitions into a worryingly Norman Bates, Donnie Darko-esque figure, in a confident performance by Schwarzenegger that grows more unsettling as his hold over Luke solidifies.

Luke’s developing relationship with Cassie is what brings many of Daniel Isn’t Real’s most interesting themes to centre stage: men’s treatment of women – from the violent sex that Daniel (as Luke) has with Sophie (Hannah Marks) to the tender love scene Luke shares with Cassie – and the mirroring of mental illness and of horror, as well as the fear and confusion that comes with it.

The film is at its best when it remains ambiguous as to what Daniel is. Is he a hallucination? A supernatural demon? A ghost? Luke’s Id? Much of the entertainment factor is derived from trying to figure out the answer. And despite the excellent visuals and effects (particularly when considering the very limited budget), the enjoyment recedes when Mortimer answers that question for the audience.

Daniel Isn’t Real is entertaining throughout and features very solid performances from its young cast, but it doesn’t quite pack the punch it thinks it does.

Daniel Isn’t Real releases in UK Cinemas 7th February, and on Blu-ray and Digital HD on 10th February.