New mother Jessica Alba is returning to work after giving birth to baby daughter Honor - to play a mathematics genius in a new movie.

Three months after she welcomed her first child with husband Cash Warren, Alba has signed to star in Invisible.

She will play "a young woman who has retreated into the world and is consumed by number and math," reports Daily Variety.

Alba won the role after Ugly Betty commitments forced America Ferrera to pull out.

The 27-year-old is also preparing to reprise her role in a sequel to 2005 movie Sin City.