After giving birth to twins, Julia Roberts is getting set to make her acting return at a stage show for children with serious illnesses - for free.

The "Pretty Woman" actress will join Paul McCartney and Robin Williams at a star-studded benefit for Paul Newman's Hole in the Wall Camps -- the world's largest association for children with serious illnesses.

The full details of the event, co-produced by veteran entertainer Lou Adler, are being kept a closely guarded secret.

But Roberts is expected to team up with Newman for one of the evening's dramatic turns.