Guess which Woody Allen movie the following scene is from: A man and woman, attending some lovely English garden party, encounter a third guest. This guest asks the two what their favorite Greek tragedy is; one earnestly cites a work of Euripides while the other — a phony — mumbles some nonsensical answer. Ah, the pretense and fraud of high British society!

If you guessed “Match Point,” you guessed wrong. The answer: “Cassandra’s Dream,” Allen’s new directing project — also set in England, also concerned with social currency and deception. It opens elegantly, with simple white credits on a black screen and original music by Philip Glass, one of today’s more influential composers. The opening suggests grand Old Hollywood (Audrey Hepburn or Cary Grant could appear at any minute), but this scrim comes crashing down when Ewan McGregor and Colin Farrell appear on screen instead.

The two English brothers are attempting to buy a boat from a gnarled old mariner and soon scrape together just enough money — earned or otherwise — to buy the tiny vessel. Terry (Farrell) had a good day at the races and suggests naming it after his winning bet: Cassandra’s Dream. Ian (McGregor), though more serious than his mechanic brother, agrees to the whimsical name. With their new boat, barely big enough to stand in, Ian and Terry are convinced their lives have taken a turn for the better.

“Cassandra’s Dream” is about the changing fortunes of these two brothers and the capricious factors that weave in and out of their lives. Both struggle financially and lack momentum in their careers. Their parents are downtrodden and can’t help them out. In scenes around the dinner table, only one thing manages to cut through the yellow palette, the wrinkled, greasy faces and the unappetizing food: Uncle Howard (Tom Wilkinson). His name trips off their H-dropping tongues (’ave you ’eard? ’oward’s coming ’ome!) and carries with it promises of a brighter future. Howard’s name sends the family into raptures, and you begin to wonder what it is, exactly, this guy does that makes him so God-like.

His arrival seems fated, and good old Fate pops up repeatedly in the movie. An alluring damsel perches roadside with a broken-down car, a family member calls in a favor, card games are won and lost: Motifs suggest divine intervention in the context of the everyday. Ian and Terry have distinct attitudes toward these occurrences; lucid, clear-eyed Ian, with ambitions of moving stateside and running hotels, wants to make his own fate, while dopey, pill-popping Terry will simply take what he can get. Wilkinson, who rocked the role of lunatic lawyer Arthur Edens in last fall’s “Michael Clayton,” plays the disappointingly diffident Uncle Howard; his arrival galvanizes Ian and Terry’s differences. When he asks the brothers, in Corleone fashion, to do him a hefty favor and repay him for all his past kindnesses, they react to it in opposite manners and bicker for the rest of the movie.

With the plot shoved into motion, the characters proceed to do a lot of talking. Nearly every scene centers around dialogue (silence is very rare), but exchanges fail to snap, crackle or pop. Farrell acts like one on stage playing to the nosebleed section: His gestures are larger-than-life, but this largeness renders them more ridiculous than effective. Stars deliver their lines like bored postmen.

The script is entirely that — scripted — and no real chemistry or engagement materializes. This is the movie’s biggest and most glaring flaw: When 90 percent of screen time is given to Farrell and McGregor clutching whiskeys and arguing with each other, the arguments had better be witty. Almost always, they are not.

Other characters dip in and out of the Terry-Ian continuum, but they routinely come off as stereotypical. Terry’s girlfriend, Kate, is the droopy blonde counterpoint to Ian’s stage-actress lover, the smoldering and dark-eyed Angela. Parents loudly nag their children. Angela’s snobby, cerebral friends scoff at her ignoramus boyfriend. With the clueless brothers at the center and their two-dimensional associates dabbling around them, the story degenerates into silly, unconvincing nonsense.

“Cassandra’s Dream” does not lack strong, obvious themes; we catch on pretty quickly to the Machiavellian versus the principled, the slick businessman versus the honest blue-collar and so on. What it does lack is a center of gravity. The plot is flimsy and the actors are less than stellar. The score is good and there is, of course, the Woody Allen stamp on the marquee, but the movie can’t really be saved. And maybe Allen should have known this from the get go: When the movie is named after a boat, which is named after a bet in a race, too much is left up to chance — a bad idea for any director.