Suffer the helpless children – suffer most horribly.

The evil spirit which haunted Israeli-born filmmaker Oren Peli’s 2009 low budget horror Paranormal Activity is back and this time, things go bump in the nightmares of two little girls with an imaginary friend, who is terrifyingly real.

Structured once again as found footage, the third film in the series is probably the least scary of the unholy trilogy, employing many of the same shock tactics as its predecessors.

However, directors Henry Joost and Ariel Schulman, who made the acclaimed documentary Catfish about the perils of social networking, deliver several jolts without plastering the screen in lashings of blood and gore.

Paranormal Activity 3 traces the malevolent force that haunts sisters Katie (Katie Featherston) and Kristi (Sprague Grayden) back to its origin.

The film opens in March 2005 in Carlsbad, California, with Kristi heavily pregnant and painting the nursery a fetching shade of blue.

Her sister arrives and asks to store two old boxes in the basement, one of which contains numerous VHS cassettes marked with the girls’ names.

Curious.

The film rewinds to Sep 3, 1988, and the birthday party of young Katie (Chloe Csengery).

Her younger sister (Jessica Tyler Brown) keeps to herself, talking to an imaginary friend called Toby.

The girls’ mother Julie (Lauren Bittner) has a new boyfriend, videographer Dennis (Christopher Nicholas Smith), who becomes intrigued by strange sounds in the family home.

‘It’s a new house.

It shouldn’t be making these noises,’ he mutters ominously, setting up two cameras, each able to record six hours of grainy footage onto VHS.

Nothing much happens on the first night, Sep 10, 1988, but as with the earlier films, events become increasingly sinister.

Julie interrogates Kristi about Toby and the girl responds calmly, ‘Why don’t you ask him yourself? He’s standing next to you.’ Soon after Dennis’s pal Randy (Dustin Ingram) speaks for us all when he warns, ‘This isn’t Casper the Friendly Ghost you’re chasing.

This thing is dangerous!’ Paranormal Activity 3 is an assured opening chapter in the horror mythology, sowing the seeds of terror in childhood that reap such rancid fruit for the sisters in later years.

The third film starts gently and apart from a couple of cheap surprises, the knot of tension in our stomachs doesn’t begin to tighten until the halfway mark.

Joost and Schulman follow the template of earlier instalments, from doors that open or slam shut without warning to bedclothes that ripple until the control of invisible forces.

The directors’ most novel conceit is perching the camera atop a rotating electric fan, allowing the field of vision to turn slowly through 90 degrees, thereby giving us a panoramic view of the family’s living room and kitchen.

More than once, we glimpse impending doom on the edge of the screen just as the fan begins to turn, and for the next 15 seconds our imaginations whir feverishly into overdrive as we contemplate what horrors are unfolding just off screen.

Only when the fan glides deliciously back to its starting point are we afforded another fleeting shot of chilling reality.

Now you see it…

now you don’t.

Boo!

• Release Date: Friday 21 October 2011
• Certificate: 15
• Runtime: 84mins