"Better Living Through Chemistry" landed at No. 13 on the 2010 Blacklist (PDF), which describes the film thusly:
A straight-laced pharmacist's uneventful life spirals out of control when he starts an affair with a trophy wife customer who takes him on a joyride involving sex, drugs and possibly murder.
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Renner, of course, is the pharmacist, with Garner as the trophy wife and Monaghan presumably as Renner's wife. And according to a reading done by Script Shadow (hat tip to Collider), the film is narrated by Judi Dench, that is, Judi Dench the actress will be portraying Judi Dench the narrator. Got that?
We love the casting. Monaghan is one of the great wasted talents of her generation (we fear she may be wasted here again as "the wife," as she was in "Due Date") and Garner's done some impressive work in film's like "Juno" and "The Invention of Lying."