What's a prosperous '40s gent to do with a wife and a mistress?

A long-married couple walk to their customary Sunday lunch at their grown daughter's house, strolling through their manicured neighborhood. Happy with the lovely day and the comfort of the familiar routine, the wife reaches out impulsively to hold her husband's hand. After a pause — just an instant too long — he takes it.

"Married Life," Ira Sachs' smart, elegant tale of marriage and its flip side (based on the 1953 John Bingham mystery novel "Five Roundabouts to Heaven"), is filled with just such subtle moments; its actions take place between the lines. Set in 1949 and filled with characters who look well-oiled and prosperous, it's the story of Harry Allen (Chris Cooper), of whom we're told in an early voice-over, "He's married. He likes his wife. It can happen."

Yes, Harry does like his wife, Pat (Patricia Clarkson), but he also likes Kay (Rachel McAdams), the chicly wistful young widow who's his mistress — so much that he launches a plot to murder Pat, so she won't have to endure the pain of being left by her husband. All this is wryly observed by the Allens' friend Richard (Pierce Brosnan, who looks terrific in '40s fedoras), who complicates matters by falling for Kay himself.

Sachs has assembled a stellar ensemble cast, and much of the pleasure of "Married Life" is watching the subtle detail the actors bring to their roles. All of Cooper's lines seem precisely rehearsed and meticulous, because Harry is exactly that kind of man. Clarkson's Pat is a very specific and unusual blend of wryness and fragility; there's a lovely moment where she sits, alone, having dinner at a perfectly set table. Brosnan exudes a Cary Grant-ish bonhomie, while McAdams is both dainty and knowingly sexy. (Watch how she casually — or not-so-casually — removes a cigarette ash from her tongue. She knows you're watching.)

Where "Married Life" struggles a bit is in its tone: Sachs seems to have set out to make at once a film noir, a Douglas Sirk-ish melodrama, a satire and a murder mystery. The movie has all of these elements, but no one genre seems to dominate, and when it's over the film still feels a little unfinished, as if the script needed one more draft. But nonetheless, it's a pleasure to watch, from the gorgeous autumnal colors of the costumes and sets to the smoky tones of the cast. "To life!" says Cooper in a toast at the end, with a surprised and infinitely complicated smile.

Moira Macdonald: 206-464-2725 or mmacdonald@seattletimes.com