The movie version of "Same Time, Next Year," opening today at area theaters, certainly takes all the glamor out of adultery. If every clandestine affair promised to be as stubbornly lackluster as the 26-year tryst that allegedly stimulates Doris and George, the harmless middle-class cheaters imagined by Bernard Slade, marital fidelity could be taken for granted.

Having missed several productions of Slade's enormously successful play, I can't tell if the wet-blanket effect was there from the beginning or merely slipped into the film version, adapted by Slade himself and directed with peerless torpor by Robert Mulligan. The consensus among trustworthy theatergoers seemed to be that the play was utterly synthetic stuff redeemed by the humorous dexterity of the performers.

On stage actors frequently succeed in investing more personality and humanity in would-be adorable numb-skulls like Doris and George than the playwright did. They also can control the space they occupy and the rhythm of the performance to an extent impossible on film, where actors are ultimately at the mercy of the cameraman, the director and the editor.

Ellen Burstyn amused thousands of theatergoers and won a Tony Award originating the role of Doris. Looking at her recreation of Doris in the movie version, it's impossible to perceive what the acclaim could have been about. She doesn't sparkle within the stodgy, leaden-footed framework imposed by Mulligan, who builds in such an abundance of dead air that you suspect he must have anticipated gales of laughter at the end of every line. Alan Alda, inheriting the role of adulterous hubby created by Charles Grodin, shares her misfortune. It's possible that Burstyn and Alda were a joy to behold on the set, but they're overexplicit and uncoordinated on the screen. They don't look amusing together or set each other off in irresistibly funny or appealing ways.

Slade lifted the structure of his play from Jan de Hartog's 1951 marital comedy-drama "The Fourposter," in which the ups and downs of a couple were distilled in six scenes covering a time period of 35 years. Doris and George first meet in 1951 at a picturesque Northern California inn (Heritage House, which overlooks the Pacific Ocean in the small town of Mendocino). She is on a weekend religious retreat, while he is relaxing after a rough week balancing a client's books.They find their brief encounter so sexually satisfying that they decide to renew the affair one weekend every year. Doris returns to husband Harry in Oakland and George to wife Helen in New Jersey. We pick up the reunions at five-year intervals, theoretically allowing Slade to reveal how life and fashion have changed the lovers in the meantime.

The obvious switch on the formula of "The Fourposter" is that the characters aren't married to each other. However, this innovation couldn't be more perfunctory. Despite having nothing particular in common, Doris and George end up resembling the dullest devoted married couple you'd ever like to avoid.

The pretense of an adulterous liaison between characters who sound like sit-com husband-and-wife may have been a complacent key to the play's popularity. Infidelity is a tease in "Same Time, Next Year." Doris and George embody a marital relationship as surely as the characters in "The Fourposter."

Slade maintains the pretense pretty shamelessly. Although Doris and George reunite only one weekend a year, their affair is treated with sticky reverence, as a kind of exemplary quickie. Over the far-flung years their weekend relationship supposedly ripens and mellows into something better than marriage -- unacknowledged marriage.

One scene ends with a frantic George finally settling down to deliver a pregnant Doris' premature baby. A rift in the mid-'60s is healed when an uptight George reveals to a hippie Doris that his son has been killed in Vietnam. When he says, "I've never shed a tear; for the life of me I can't seem to cry for him," you know it's only a matter of minutes (seconds actually) before the curtain rings down with George achieving a cathartic weep on Doris' understanding shoulder.

Slade's flair for nifties may be gauged by the following exchange in the opening scene:

George: We had instant rapport. Did you notice that?

Doris: No, but I knew that we hit it off right away.

His heartwarming number goes something like this:

George: When did I suddenly become so appealing?

Doris: When you went from pompous to confused.

A little laugh, a little tear, a gotcha here, a gotcha there. A formula romantic comedy rarely complicated by a hint of integrity or credibility, "Same Time, Next Year" proves that Slade can write gotcha kitsch with the worst of them.