"Making Love" begins with a lingering study of Michael Ontkean's blandly handsome mug. A few seconds later, equally imposing images of Kate Jackson and Harry Hamlin swim into view and, speaking directly to the camera, share confidences about a certain Loved One. If you don't know what the movie is about, their remarks could be misconstrued as comments about each other. This impression is soon revealed to be a sly tease on the part of screenwriter Barry Sandler. In fact, Jackson and Hamlin are recalling a mutual love object -- Zack (Ontkean) -- with rueful tenderness.

But one of the abiding mysteries of "Making Love," which opens today at area theaters, is the devastating charm exerted by Ontkean's character, an earnest young internist named Zack Elliott, on the characters played by Jackson and Hamlin -- Claire Elliott, Zack's adoring and unwitting wife, and Bart McGuire, a promiscuous homosexual writer. What is it about this mild-mannered, conventional-minded Young Doctor that makes him such a heartbreaker?

"Like Zack," screenwriter Barry Sandler has revealed, "I was involved in a relationship with a woman, and we were close to getting married. When I realized that my attractions were toward other men, I went through a period where I thought, maybe I'm just experimenting, maybe I can continue with both relationships. But you can't. You can't continue to deny or block out what you really feel . . . Bart represents another side of me -- and the side of many of us, straight or gay -- that wants to float free and not get too deeply involved with anyone . . . I tapped into and clarified my own personal anxieties, fears and confusions . . . It was very much an unleashing process which ultimately proved to be the most fulfilling experience I've had as a writer."

Without questioning his sincerity, one may still regret the synthetic feebleness of Sandler's perceptions and skills. He contrives an extremely volatile sort of emotional triangle around three characters so stilted that they can't possibly embody strong passions and messy betrayals.

In addition, "Making Love" is set in a maddening, artificial southern California environment where a prosperous, career-centered young couple like Zack and Claire can show off their cultural superiority on the strength of a smug fondness for Gilbert & Sullivan and poet Rupert Brooke. Here, Zack can compliment Bart on his literary style by saying, "Good tough writing," and Claire can be mistaken for "the sharpest brain" in television because she cares about "quality" programming.

Zack and Claire are such emotional knuckleheads that it's impossible to play along with the pretense that they share a close marriage before Zack begins acting on his mysterious impulse to pick up guys. Also, insufficient attention is paid to his apparent sexual estrangement from Claire while the filmmakers rev up for their daring moment -- the petting scene between Ontkean and Hamlin. Obviously, a key aspect is being overlooked while another aspect is being discreetly exploited for novelty oohs-and-ahhs.

I'm sure Sandler never realized what a colossal stupe he made Claire. The revelation scene is astutely set up, with poor trusting Claire assuring Zack, "I can handle it, whatever it is." Well, she can't, and one of the few genuine, encouraging emotional responses in the picture documents her instinctive outrage at Zack's sexual betrayal. Although it's a sure-fire theatrical situation, the scene also owes a lot to Jackson, who seems peculiarly effective as a woman who is suddenly liberated by a delayed-action flash of comprehension. Claire acquires a touch of dignity when she kicks Zack out of the house.

Unfortunately, Claire never seems seriously hurt, anymore than Zack seems seriously torn in his affections. Shortly after the blowup, Sandler has Claire begging Zack for a fresh start and even offering to transcend sex if only they could sustain their marriage. Having achieved his own erotic breakthrough, Zack nobly demurs, reminding Claire ever so generously, "You're entitled to a good sex life."

Now friends, Zack and Claire treat each other with a nobler-than-thou solicitude. Bart gets off easy too, of course, but one feels relieved on his behalf that he won't have Zack mooning about for years to come. An all-choked-up epilogue assures us that everything comes up contentment for Claire and Zack with their future partners. Still, it's difficult to tell whose blissful domesticity is going to provoke the bigger gales of laughter.

Of course, the choicest union is Barry Sandler and director Arthur Hiller, a blend of earnestly naive sensibilities that may never be surpassed in contemporary Hollywood.