Since making a huge international splash with their torture flick Saw, back in 2004, Malaysian-born director James Wan and Australian writer/star Leigh Whannell have had a bumpy ride in Hollywood. Financially, neither of them need ever work again, having been involved as executive producers in all six sequels to their insanely successful horror franchise, but attempts to branch out and try something new have been less successful. Dead Silence and Death Sentence (both 2007) failed to make much of an impact, and now they try once again to recapture lightning in a bottle with Insidious. As always, Wan directs, while Whannell writes and co-stars, albeit in a significantly smaller role than in Saw.

The film follows the Lambert family as they move into a new suburban home, only to soon suspect that it may be haunted. Following a strange noise up into the attic, their young son Dalton (Ty Simpkins) suffers a minor accident but winds up in a coma. The doctors allow Dalton to be cared for at home, but his presence only increases the bizarre sightings, voices and supernatural disruptions in the house. Their younger boy, Foster, even claims that he sees Dalton sleepwalking. After traditional medicine fails to help and even moving house doesn’t solve their problems, distraught parents Josh (Patrick Wilson) and Renai (Rose Byrne) turn to less conventional sources for help.

Insidious is a huge step away from the ghastly sadism of Wan & Whannell’s previous work, relying here almost entirely on mood and atmosphere to deliver the scares. For the first half, Insidious is a slow build of increasingly uncomfortable and disconcerting events that effectively crawls under the skin of even the most season horror fan. Too often recent horror relies on loud noises, fast editing and copious amounts of blood and gore to get a reaction from its audience, so this return to old school atmospherics is a most welcome one. Films such as Tobe Hooper’s Poltergeist are obvious points of reference, but Joe Dante’s The Hole also shares many structural similarities. The invasion of the home by unseen spirits that cannot be easily defeated or understood taps into a very primal fear, that is only heightened when the children are targeted and then suggested as being complicit with the impending threat.

It is a great disappointment, therefore, that Wan and Whannell fumble the third act so spectacularly. As with Dante’s film, or Victor Salva’s Jeepers Creepers, we are scared of the unknown. Once the curtain is pulled back, the threat is identified and our heroes are mobilized against it, that uncertainty and helplessness is lost and we are left with a fairground ride or Halloween costume party, which frankly just isn’t scary. Sadly, Insidious ends in a final half-hour of unraveling tension and preposterous resolution that will leave viewers irritated and even unintentionally amused, rather than gasping for breath. Insidious still deserves a recommendation for its excellent first hour, but ultimately will leave you lamenting what might have been.