Sam Rockwell is in negotiations with Occupant Films to star in the black comedy/thriller Better Living Through Chemistry. Jeremy Renner, who was previously slated for the role, has jumped ship to maintain a slightly more manageable schedule (he is currently on board Mission: Impossible - Ghost Protocol, The Avengers, and The Bourne Legacy, just to name a few). Starring opposite Jennifer Garner and Michelle Monaghan, Variety reports that Rockwell will play a small town pharmacist whose unhappy marriage (to Monaghan) leaves him vulnerable to the alluring wiles of a sexy trophy wife (Garner) and the highs of prescription drugs. Chaos breaks loose when their affair escalates and the unfaithful couple hatches a plot to murder her husband. The film will be a debut feature from writer-directors Geoff Moore and David Posamentier. Judi Dench is on board to narrate the pic. Hit the jump for more on Rockwell and Better Living Through Chemistry.In some ways it's a pity that Jeremy Renner had to drop Better Living Through Chemistry - an actor that talented is a boon to any production lucky enough to have him. That said, I won't deny that, as an unashamed fanboy of Sam Rockwell, I'm excited about this new casting. Rockwell has proven time and time again that there's no role that won't succumb to his skills. Following on from his recent turns as smooth operator Justin Hammer in Iron Man 2 and innocent inmate Kenny Waters in Conviction, Rockwell has been shooting Cowboys & Aliens back alongside Jon Favreau, and will also star as a dealer in David Gordon Green's drug addled comedy The Sitter with Jonah Hill. Aside from his relatively recent casting in Seven Psychopaths and Cogan's Trade, though, his upcoming schedule wasn't exactly looking packed. It's good to see some new titles falling in to his lap.Now, you may never have heard of Geoff Moore or David Posamentier, but if you happen to follow unproduced Hollywood scripts much (actually I don't either), then you may recognize their names from the 2010 Black List. Their screenplay for Better Living Through Chemistry scored pretty highly with the Hollywood execs, slotting in at number 17, and it's a list which carries a lot of weight, with numerous past films like Juno, Little Miss Sunshine, Lars and the Real Girl, 500 Days of Summer and The Social Network eventually getting a release (to name but a very scant few).Although the concept isn't exactly highly original - the affair that turns deadly must surely be one of the most recycled plot lines - this could prove an interesting take, and so far the decent casting is boding well for the film. Certainly Michelle Monaghan, starring as Rockwell's wife, expressed her early excitement about the movie, telling The Playlist, "It's a really great film" and describing her character as "really anal" and "uptight".That's all very auspicious, but I'm not sure Judi Dench will necessarily be sharing the same enthusiasm. Cast as narrator, we already expressed some doubt about the necessity of her role, and on a personal level I'm disappointed that such a superb actress has effectively been delegated voice over work. Having said that, it's far too early to start hurling criticism, particularly with such little to go on, and we'll have plenty of opportunities to admire Dench in upcoming projects including the much-anticipated J. Edgar.