THERE'S A QUIET apocalypse going on in "Longtime Companion" that is subtly but utterly devastating. It begins with a 1981 New York Times article that speaks of a "rare cancer" in the gay community. Then it methodically goes about its grim business, stealing the breath of young men.

Made by playwright Craig Lucas and director Jim Rene for American Playhouse Theatrical Films, "Companion" has one thing on its mind: a message, a call to consciousness. But it is precisely the omnipresent, real-life implications behind the movie, the things we know -- or don't -- beyond this film, that gives "Companion" its power.

Looked at clinically (as AIDS all too frequently is), "Companion" has certain dramatic shortcomings, and is rife with propaganda. It's every bit the product of an American Playhouse production, in which the characters are decent, well-intentioned urban professionals, whose minimal shortcomings are essentially the result of innocence. With the exception of an episode in which a Latino AIDS patient is sullen and resentful towards his volunteer "buddy," the characters tend to band around each other a little too didactically, and seem far better people than many of us.

But the clinical approach seems irrelevant in this case; "Companion" also has more than its share of dramatic strengths. There are some tremendously assured performances, particularly from Bruce Davison who, as the tenacious supporter of his dying lover, exudes an understated serenity. Campbell Scott as the main character, who goes from idle innocence to outright advocacy, is empathetically on the money. Dermot Mulroney also does a great deal in a small cameo.

Lucas, who wrote the plays "Blue Window," "Reckless" and "Prelude to a Kiss," has a deft bedside manner that mixes in humor with the sadness. When, for instance, a doctor asks bedridden patient John Dossett to identify the president, he replies "Ronald Reagan." When the doctor asks him to identify the vice president, Dossett says "Nancy Reagan."

Lucas also adds some true, pathetic touches. When visiting and kissing a sick friend in the hospital, for instance, a panicked Scott retreats into the bathroom to wash his hands and mouth secretly and thoroughly.

Recommending this movie to gay audiences seems a waste of time, since there is every indication this picture will bring people from that community together. As characters die, and they will die, the names and faces of real, loved ones will come to a lot of minds.

Presumably, what counts most is "Companion's" palatability for non-gay audiences. The movie puts a human face on the AIDS scare and gently coaxes general audiences (at least, the open-minded variety) into rooting for, rather than fearing, people with AIDS.

Given the greater epidemic of AIDS ignorance throughout our society, this film is a healthy dose of goodwill.