And the box office champion this week is...

LOS ANGELES – Fear has taken hold at the box office with a $41.5 million debut for scary movie "Paranormal Activity 2," according to studio estimates Sunday.

Paramount Pictures' follow-up to last year's micro-budgeted hit "Paranormal Activity" got a jump on Halloween as fans packed theaters for another documentary-style thriller about a household plagued by a menacing spirit.

"Paranormal Activity 2" did nearly half its business on Friday, following the pattern of many fright-flick franchises, which often draw big crowds on opening day then drop off sharply. The movie took in $20.1 million Friday, with receipts falling to $13 million Saturday and $8.4 million Sunday.

The first "Paranormal Activity" rolled out gradually from city to city in a stealth-marketing campaign that built the buzz for the independently produced thriller that was shot for less than $15,000.

By the time the movie went into nationwide release, it had turned into a horror sensation that went on to become a $100 million hit.

The first movie came out of nowhere, and follow-up films to similar surprise smashes sometimes fall flat, such as "The Blair Witch Project" sequel. In its publicity campaign, Paramount tried to maintain an air of mystery around "Paranormal Activity 2."

"The challenge was to not make the mistake of some other movies of the past, and to treat it as its own very special entity. Even though we went wide with it, we tried to treat it a lot like the first one was treated from a publicity and marketing standpoint," said Don Harris, the studio's executive vice president for distribution.

Paramount also had the No. 2 movie with the stunt comedy "Jackass 3D," which opened in first place the previous weekend. "Jackass 3D" pulled in $21.6 million, down sharply from its $50 million opening.

But the movie raised its 10-day total to $87.1 million, more than either of the earlier two "Jackass" movies took in during their entire runs.

Summit Entertainment's action comedy "Red" held up well from its No. 2 debut a weekend earlier, slipping to third with $15 million and lifting its 10-day total to $43.5 million.

After opening Clint Eastwood and Matt Damon's "Hereafter" in limited release a week earlier, Warner Bros. expanded the supernatural drama nationwide, and the film came in at No. 4 with $12 million.

That slightly exceeded the studio's expectations, yet like most Eastwood dramas, it was a modest start. His films play to older adults who do not rush out on opening weekend in the same numbers as young crowds.

"Clint's movies these days are more of a marathon than they are a sprint, so we'll see how it plays out," said Dan Fellman, head of distribution at Warner. "I always tell Clint, `Let's not talk about the first weekend. Let's talk about the third.'"

"Hereafter" played well in bigger cities but delivered softer business in some parts of the South and Midwest. That could be a sign that Bible Belt areas were not as interested in "Hereafter," which deals with the afterlife in secular fashion without bringing God or religion into the picture.

The big opening for "Paranormal Activity 2" sets up a rematch of last Halloween season, when the first "Paranormal Activity" dismembered an established horror franchise and "Saw VI" debuted weakly with the worst opening weekend in the series' history.

Lionsgate went back to the drawing board for the seventh "Saw" movie, opening this Friday. "Saw 3D" brings back Cary Elwes from the franchise's first movie and mixes other cast members from throughout the series, while trying to capitalize on fan appetite for flicks shot in 3-D.

"This is a bigger, more powerful `Saw,' so to speak," said Paul Dergarabedian, box-office analyst for Hollywood.com. "It kind of primes up audiences for a major Halloween smackdown battle of the horror films, but I think `Saw 3D' is going to be a much more formidable opponent."

Estimated ticket sales for Friday through Sunday at U.S. and Canadian theaters, according to Hollywood.com. Final figures will be released Monday.

1. "Paranormal Activity 2," $41.5 million.

2. "Jackass 3D," $21.6 million.

3. "Red," $15 million.

4. "Hereafter," $12 million.

5. "The Social Network," $7.3 million.

6. "Secretariat," $6.9 million.

7. "Life as We Know It," $6.2 million.

8. "Legend of the Guardians: The Owls of Ga'Hoole," $3.2 million.

9. "The Town," $2.7 million.

10. "Easy A," $1.8 million.