Paranormal Activity 3

Some of the known laws of physics are defied in “Paranormal Activity 3,” but the law of diminishing returns is in full effect. The problem of how to satisfy returning viewers without merely repeating what you’ve already done is a tough one to solve anyway (which is why most sequels don’t bother trying), and it’s especially tricky when, as with “Paranormal Activity,” there’s such a specific and narrowly defined style. If you break out of the central conceit of people using video cameras to capture spooky nocturnal proceedings in their house, then it’s not really a “Paranormal Activity” movie anymore. But what more is there to be done within those confines?

The answer, apparently, is that there isn’t much “more” to be done — and that it doesn’t really matter. “Paranormal Activity 3” shows that if coming up with new magic tricks isn’t an option, performing the old tricks with flair will suffice. For a while, anyway.

We learned over the course of the first two films that sisters Kristi and Katie had encounters with supernatural forces when they were children, and now part 3 shows those events to us, as they occurred back in 1988. This is feasible because, as it happens, the girls’ stepfather, Dennis (Christopher Nicholas Smith), was as diligent about videotaping weird phenomena as their future husbands would be.

Young Katie (Chloe Csengery) and Kristi (Jessica Tyler Brown) are about 8 and 6 when weird stuff starts happening in their normal, modern suburban home. Dennis accidentally captures something unusual on tape, and is further inspired by Kristi’s reports of having an invisible friend named Toby. He sets up cameras in the girls’ bedroom, plus one in the bedroom he shares with their mom, Julie (Lauren Bittner), who rolls her eyes at the whole thing but humors him.

This being 1988, video technology is expensive and not very sophisticated. (It is, curiously, in widescreen, though.) Dennis mounts a third camera on an oscillating fan so it can constantly move back and forth between the living room and kitchen. This eliminates the need for a fourth camera, and also gives the filmmakers a nifty device to creep us out with: the camera shows us the kitchen; pans slowly to the living room; pans slowly back again — AND NOW THERE’S SOMETHING IN THE KITCHEN! As in the previous installments, the special effects are low-tech and practical rather than computer-generated: hidden wires, sleight of hand, subtle editing tricks.

Christopher B. Landon (son of Michael Landon!) returns from co-writing part 2 to get sole credit on part 3. He’s joined by an inspired choice of directors: the team of Henry Joost and Ariel Schulman, who made “Catfish,” an alleged documentary that some people are convinced was fake. The “Paranormal Activity” films are the reverse of that — nobody’s actually trying to fool us into thinking this is real footage — but Joost and Schulman’s experience with straddling the line between fact and fiction comes in handy.

And they do a good enough job executing the scares, both subtle and overt, that are the franchise’s hallmarks. It’s just that they’re the same scares we’ve already seen, separated by the usual gaps of ordinary life that the series’ detractors find so boring. Mounting a camera on a fan is neat and all, but it shouldn’t be the primary innovation of your sequel. So even though the jump scares still got me, and even though the movie is goosebump-y enough to be recommendable, I suspect this is the last time it’s going to work unless they get some new ideas.

B- (1 hr., 25 min.; R, a little sexuality, some harsh profanity, general scariness and stuff.)