Rooney Mara has signed up to star in 'Trash'.

Both 'The Girl With the Dragon Tattoo' star and Hollywood veteran Martin Sheen have signed on to appear in the film, adapted from the 2010 novel by Andy Mulligan and to be directed by Stephen Daldry.

The story centres around three homeless orphan boys in a non-specified third-world country in the near future, who sift through a huge trash heap in search of things to sell to survive.

The adventure sees the boys - played by newcomers Rickson Tevez, Eduardo Luis and Gabriel Weinstein - find a leather bag containing a wallet with money and an ID card, a map and a key. This discovery plunges the trio into a murky underworld and onto a bigger path of discovery which sees them have to negotiate with corrupt officials and unsavoury characters at every turn.

Helping them along the way are Sheen's character, Father Julliard, a priest who takes them in, and Mara's Non Governmental Organisation (NGO) worker.

The story has been adapted for the screen by 'Four Weddings and a Funeral' director Richard Curtis, and production is due to begin in Rio de Janeiro, Brazil, next month.

The film is tentatively scheduled for a May 2014 release.