(M) ***

Director: Ariel Schulman and Henry Joost.

Cast: Lauren Bittner, Christopher Nicholas Smith, Chloe Csengery, Jessica Tyler Brown.

I HAVEN'T seen the previous Paranormal Activity films, but that's probably not a bad thing because this one is a prequel, so maybe I've started in the right place, right?

What I can tell you is that there are some good heart-starting jumps in this third outing of the popular found-footage horror series to make it worthwhile, even if you haven't seen the Oren Peli original or its follow-up.

Predominantly set 18 years before the first film, the action takes place on an old video cassette made by wedding videographer Dennis (Smith), who was dating Julie (Bittner), the mother of Katie (the main character in the other two Paranormal Activity movies).

After Dennis, Julie, Katie (Csengery) and youngest daughter Kristi (Brown) moved into a new house, they noticed some strange happenings, starting with them accidentally filming an earthquake and seeing something odd in the footage.

Dennis set up video cameras around the home in the hopes of capturing more bizarre occurences, which he thinks might be connected to one of the girls' imaginary friends. But what other family secrets does the videotape contain?

While the "scary home movie" has been done a lot since The Blair Witch Project sucked in and freaked out audiences in 1999, Paranormal Activity 3 at least uses its format well, keeping things reasonably sensible in the face of increasing weirdness.

Schulman and Joost, who artfully pieced together the intriguing Facebook doco Catfish, ramp up the scares well, starting out with the suggestion of strangeness and even a few fake "boo!" moments before building the film into a genuine pants-wetter.

The movie rides a fine line between boring and suspense-building at times, but the last few minutes more than make up for any slow patches and will have you rivetted.

The performances are nicely naturalistic across the board and the special effects are unobtrusive, perhaps because any seams are well hidden by the video format.

I'd like to say this is a worthy addition to the series but I don't know that - perhaps the best recommendation I can make is that after seeing this one, I'm interested in seeing the other two.