In a tight box office race, psychological thriller ‘Unknown’ took the top spot with $21.7 million followed by new science fiction entry ‘I Am Number Four’ with $19.5 million. The ‘Four’ filmmakers probably breathed a sigh of relief that the film took second instead of its title considering it was followed closely by Disney’s ‘Gnomeo And Juliet’ with $19.4 million and previous number one film ‘Just Go With It’ with 18.2 million.

In it’s third weekend, the James Cameron produced 3D film ‘Sanctum’ fell out of the top 10 dropping to 12th with a paltry $1.5 million.

‘The Green Hornet’ placed 14th and added an additional $1.4 million to bring its total domestic box office to $95.1 million.

The fantasy thriller ‘Black Swan’ crossed the $100 million mark, dropping just one place to 15th and adding another $1.3 million to its domestic total box office.

1. ‘Unknown’   $21.7
2. ‘I Am Number Four’  $19.5
3. ‘Gnomeo And Juliet’  $19.4 
4. ‘Just Go With It’   $18.2
5. ‘Big Mommas: Like Father, Like Son’ $17.0
6. ‘Justin Bieber: Never Say Never’  $13.6
7. ‘The King’s Speech’  $6.5
8. ‘The Roomate’   $4.1
9. ‘The Eagle’   $3.5 
10. ‘No Strings Attached’  $3.1