Ian (Ewan McGregor) and Terry (Colin Farrell) are two working-class brothers in London who dream of a better life. While Terry struggles with gambling and alcohol addictions, Ian gets a taste of the high life through his courtship of an actress (Hayley Atwell) and wants more. Looking to their rich uncle Howard (Tom Wilkinson) for financial help, Howard agrees with one condition: he wants the boys to murder a business partner with intentions to testify against him for unethical business practices. Ian and Terry, floored by the offer, now have to contemplate how much they truly want their money problems solved.

An extension of the murderous, duplicitous rampage of Allen's 2005 triumph "Match Point," "Cassandra's Dream" (named after the brothers' sailboat) tinkers somewhat with Allen's usually tip-top timing. While well-known for his meticulously arranged verbal jousting, Allen's screenplay for "Cassandra's Dream" is an atypically long-winded affair, with pages of dialog assigned to scenes where merely a few choice words or knowing glances would've sufficed. It's a hyper-lippy approach that stretches out every moment of this film; some to an agreeable swirl of confusion and reluctance, and others to painful dead-ends. It's a theatrical approach that has Ian and Terry in constant dialogue about every little step they take, debating their every impulse.

McGregor and Farrell make the material sing with their performances, using the absence of air to their great advantage. Especially Farrell, who takes to Allen's visual limitations wonderfully, demonstrating newfound abilities to convey profound anguish with a simple jitter of the eyes. McGregor has the more difficult role as the eternal optimist, which the actor turns into a beguiling used car salesman of misery. Farrell and McGregor hold believable familial chemistry and interact well onscreen, often making Allen's leaden prose sparkle.

Energy is in short supply in "Cassandra's Dream," as Allen has difficulty equalizing the thriller subplot of the story with the rest of the psychological trauma. Ian and Terry convincing themselves to commit murder is by far the most compelling corner of the story, sold vividly by Philip Glass's exquisite score. However, the build-up only brings the picture to the halfway point, and Allen takes his time exploring the aftermath of these urgent decisions. It leads to a wonderful climax that steps in the same footprints as last year's firecracker "Before the Devil Knows You're Dead," but it requires an extensive commitment of patience. Allen doesn't want to breeze through this biblical tale of wicked brothers without exploring all the possibilities of guilt, and while it can make the whisky-soaked picture feel three days long, it does nothing to dilute the essential dread that Allen writes so wonderfully.