The devil has pitched up on Charing Cross Road – and he sounds very much like Gandalf in deep distress in this stage version of the book and movie about 12-year-old Regan (Clare Louise Connolly) who unwisely plays with the Ouija board she finds in the attic and becomes possessed by a demon.

The unseen, and uncredited, Ian McKellen voices Satan, and he is the classiest thing in a show that is less head-turningly scary than mind-numbingly dull and about as spooky as a wet sock.

William Friedkin’s 1973 film unnerved a generation by turning projectile vomiting into entertainment, but you’d be more likely to call for milk of magnesia than a priest. Sean Mathias’s staging recreates some of the movie’s famous moments – including Regan’s levitation – but becomes less and less terrifying with every blackout, special effect and projection it deploys.

If this production actually managed to deliver the thrills, like a theatrical version of a fairground ghost train, you might forgive the complete lack of characterisation or the uncertainty of tone that leaves the evening awkwardly pitched between the camp and the uncanny. It grinds out the tale with jerky efficiency, like a storyboard on stage that moves not from one scene to the next but one set piece to the next.

John Pielmeier’s script goes for melodrama and stock characters, which leaves little room for any psychological depth or nuance in the performances. Jenny Seagrove wrings her hands distractedly as the mother convinced her child is possessed, and Adam Garcia as Father Damien Karras, the priest who is struggling with his own guilt and demons, looks less conflicted than if he is suffering from mild toothache. Peter Bowles’s exorcist, Father Merrin, turns up looking the part but sets about his task with all the urgency of a plumber sent to unblock a drain. Instead of building to a thrilling and terrifying climax the show limps towards its schlocky conclusion.

The far superior The Haunting of Hill House, seen at Liverpool Playhouse in 2015, proves it’s possible to reinvent the horror genre on stage combining visceral thrills with psychological acuity. The Exorcist doesn’t even try, and while the title may lure in the unsuspecting during the Halloween season the show may find itself being the one that is cast out.

• At the Phoenix theatre, London, until 10 March. Box office: 0844-871 7615.