Oscar-winning screenwriter William Monahan (The Departed) has been hired to work on the script for Sin City 2 for Robert Rodriguez and Frank Miller, who co-directed the first Sin City feature, according to Hollywood Reporter.  Monahan will be reworking a script by Miller, according to the report. 
Rodriguez said at Comic-Con that the sequel is getting close (see “Robert Rodriguez Planning Movies”), with a new Miller chapter written specifically for the film, “The Long Bad Night,” providing the storyline.