Much like its predecessors, “Paranormal Activity 3” is a slow-building, stealthily creepy supernatural thriller that takes a teasingly indirect approach to generating suspense and escalating dread. The threequel is actually a prequel, time-warping back to 1988 to show how siblings Katie (Katie Featherston in the first film) and Kristi (Sprague Grayden in the second) were traumatized at an early age by things that go bump in the night. Slightly slicker and more densely populated than earlier pics in the franchise, the Oct. 21 Paramount release should play well with any fans who haven’t already tired of the found-footage gimmick.

Although Featherston and Grayden make token appearances in a portentous prologue, preteen newcomers assume their roles throughout the rest of “Paranormal Activity 3.” Pic details how Dennis (Chris Smith), the girls’ videographer dad, becomes obsessed with discovering the source of latenight noises that echo throughout their spacious suburban home — and learning the true nature of an imaginary playmate who may not be so imaginary after all.

Again like its predecessors, the film pivots on the conceit that its elliptical narrative has been culled from videos shot by someone (or a couple of someones) who cannot be called upon to provide any sort of explanatory narration. (It’s interesting to consider whether some future sequel will identify just who’s been editing together all this spooky stuff.)

Given that Dennis usually makes a living as a wedding videographer, the new pic makes it seem a bit more plausible that the individual shooting the video (and in this case, his eager assistant) would be so adroit at setting up surveillance cameras, and so determined to keep filming long after most other folks would have fled to safer environs.

Co-directors Henry Joost and Ariel Schulman (“Catfish”), working from a script by “Paranormal Activity 2” co-writer Christopher B. Landon, pull off some ingeniously suspenseful scenes that are all the more effective for their constrained points of view. Because the camera is either stationary or handheld, the audience doesn’t always see everything it anxiously wants to see, and can only imagine the worst is occurring just beyond the frame.

Some of the scariest moments are those captured by a camera Dennis supposedly has jerry-rigged atop the base of an oscillating fan. On more than one occasion, the viewer waits breathlessly while the camera pans away from something vaguely disturbing or unsettling — and then gets seriously rattled as the camera pans back to confirm worst expectations.

Viewers who were turned off by the repeated bickering of the two leads in the first “Paranormal Activity” may have a similar response to scenes here in which Dennis tries to convince Julie (his wife and the girls’ mother) that something supernatural may be afoot, and she simply refuses to listen. A few of the franchise’s most devoted fans also may object to the new pic’s attempt to explain why Katie and Kristi turned out the way they did by alluding to the influence of a witches’ coven, a plot wrinkle that seems almost as literal-minded as those suggestions in later “Halloween” sequels that the masked Mike Meyers was supernaturally enhanced by modern-day Druids.

Despite that, however, “Paranormal Activity 3” earns points for its low-key ability to keep viewers primed over long stretches to expect that something very bad, or even worse, may happen at any moment. Pic premiered in near-complete form as a midnight secret screening at Austin’s genre-skewing Fantastic Fest, where audience response indicated that favorable word-of-mouth buzz soon may reach deafening levels.

Paranormal Activity 3

  • Production: A Paramount release of a Blumhouse/Solana Films/Room 101 production. Produced by Jason Blum, Oren Peli, Steven Schneider. Executive producer, Akiva Goldsman. Directed by Henry Joost, Ariel Schulman. Screenplay, Christopher B. Landon, based on the original film "Paranormal Activity" directed, written by Oren Peli.
  • Crew: Camera (color), Magdelena Gorka; editor, Gregory Plotkin; production designer, Jennifer Spence; set decorator, Kelly Berry; costume designer, Leah Butler; casting, Terri Taylor. Reviewed at Fantastic Fest (Secret Screening), Austin, Sept. 29, 2011. Running time: 81 MIN.
  • With: With: Chris Smith, Katie Featherston, Sprague Grayden, Lauren Bittner.