Sam (Christian Bale) and his fiancée, Alex (Kate Beckinsale) are a newly engaged couple who move to Los Angeles to further their working careers. Sam is a recently graduated psychiatrist, starting his residency, while Alex is finishing her M.D.-Ph.D. dissertation on genomics. The relatively strait-laced, upwardly mobile couple plan to stay at the vacant home of Sam's mother, Jane (Frances McDormand), a free-spirited record producer in the Laurel Canyon section of the City of Los Angeles.
In a change of plans, however, Jane is still around, recording an album with her boyfriend Ian (Alessandro Nivola) and his band. The film focuses in some depth on the challenge of trying to create successful pop music, showing work on two tracks (both actually written, and later released, by the band Sparklehorse). Ian's bandmates are played by noted indie rockers, bassist Lou Barlow and guitarist Imaad Wasif.
Jane and Ian are in the midst of a fiery romance, and both producer and band seem more interested in partying than finishing the record.
Jane's presence is a source of consternation for Sam, as he and his mother have a somewhat strained relationship owing to their very different mindsets. Alex, however, is intrigued by the new lifestyle options presented by Jane and Ian; normally hardworking, she begins spending more time with the band and less time working on her dissertation. Meanwhile, Sam finds himself attracted to fellow resident Sara (Natascha McElhone), who is unapologetically interested in him as well. The situation strains Sam and Alex's relationship almost to the point of breaking when Sam discovers Jane, Ian, and Alex engaging in a sexual threesome.
Tagline: On the road to the perfect life, Sam & Alex took a little detour.