Combine a mysterious baby and a barking dog with a $3 million budget – and what do you get? Horror’s biggest opener to date.

Paranormal Activity 2, Paramount’s follow to last year’s surprise hit, scared up a record-breaking $40.7 million over the pre-Halloween weekend. The film not only took first place away from Jackass 3D, it edged past Friday the 13th for the scream title. (That 2009 remake debuted to $40.6 million in February 2009.)

Meanwhile, Clint Eastwood’s Hereafter, which expanded from a limited release, also made entry into the Top 10. The Matt Damon-starrer settled into fourth place with a $12 million take.

1. Paranormal Activity 2, Paramount, $40,678,424 (avg. $12,649)
2. Jackass 3D, Paramount, $21,313,815 (avg. $6851)
3. Red, Summit Entertainment, $15,034,916 (avg. $4594)
4. Hereafter, Warner Bros., $12,018,147 (avg. $5510)
5. The Social Network, Sony, $7,276,972 (avg. $2491)
6. Secretariat, Disney, $7,001,159 (avg. $2253)
7. Life as We Know It, Warner Bros., $6,136,454 (avg. $2033)
8. Legend of the Guardians: The Owls of Ga'Hoole, Warner Bros., $3,248,019 (avg. $1453)
9. The Town, Warner Bros., $2,749,090 (avg. $1433)
10. Easy A, Sony Screen Gems, $1,748,906 (avg. $1072)

(You can review last week's numbers here.)