The plot is harmless enough, rife with opportunities for the Coens to inject their singular brand of humor. George Clooney, slyly funny in the Cary Grant role, plays Miles Massey, a highly respectable and successful divorce attorney who falls for his client’s ex-wife, Marylin (a ravishing Catherine Zeta-Jones). Massey is in the throes of a mid-life crisis, and he meets his match in Marylin, a cunning and aggressive Beverly Hills gold-digger who’s looking to claim half the assets of her cheating husband (Edward Herrmann).

Despite the infallible evidence of his affairs, Miles gets the husband off the hook and begins to pursue the newly single Marylin. Yet out of desperation, she engages Howard D. Doyle (Billy Bob Thornton), an oil tycoon prone to pontificating on the virtues of Texas life. She enlists Miles to administer his famous “Massey Pre-Nup” for the couple, his airtight prenuptial agreement that has never failed either divorced party.

The Coens’ standard outlandish characters populate the sidelines. Geoffrey Rush hams it up as cuckolded TV producer, replete with a yuppie ponytail and a short fuse. Cedric the Entertainer plays a surveillance expert hired by Marylin to videotape the tryst between her husband and a buxom blonde.

But I have much higher expectations for the Coens, who have never played down to their audience quite like they do here. Even the direction lacks panache this time: Massey and his assistant’s bumbling home invasion late in the film cannot compare to the minimalist suspense attained in “Blood Simple’s” conclusion. As far as the comedy is concerned, it seems like the brothers hired Danny DeVito to block the slapstick (save for a bit involving a misplaced gun and an asthma inhaler).

Maybe the fault lies in the studio collaboration. For the first time in their careers, the Coens are working off material other than their own — the story was originally authored by the talent behind “Big Trouble,” last year’s Tim Allen vehicle. And Brian Grazer, Ron Howard’s co-conspirator in Oscar-winning dreck, joined Ethan as co-producer.

The film isn’t void of merit. There are some surprising turns, and plenty of oddities and grotesqueries are on display. The script is peppered their wit and stylized dialogue.

But many of the Coens’ stabs at mainstream comedy fall flat, not to mention the uncharacteristic romantic vibe they add to the proceedings.

The directing duo have always approached their material with a charted distance, and while they’re not incapable of infusing their characters with humanity (like the protagonists of “Fargo” and “Miller’s Crossing”), their failure to do so in this film renders the coda maudlin and the comedic bluster empty.