Terrence McNally sets out to cover a lot of ground in "Mothers and Sons," now receiving its Austin debut at Zach Theatre.

In just 90 minutes, the Texas-born multiple Tony Award winner touches on the complex legacy AIDS has left on the gay community; the relationship between gay men and their parents (mothers in particular); and how the past several decades have resulted in enormous changes in the gay community — same-sex marriage, first and foremost — that, while positive, have nevertheless produced big generational schisms.

The plot whiffs of more than a little artifice.

On a snowy day shortly before Christmas in 2014, Katherine (Michael Learned) arrives unannounced at the upscale Central Park West apartment of Cal, the former boyfriend of her deceased son, Andre.

Self-absorbed, resolutely bitter in her fur coat, Katherine is looking to lash out at someone, trying to reconcile why her son died of AIDS two decades previously. ("Mothers and Sons" is a sequel to McNally’s 1990 PBS teleplay "Andre’s Mother," set at Andre’s memorial service.)

Mostly, though, Katherine is unable to forgive Andre for being gay and seems to have arrived improbably at Cal’s doorstep for — well, it’s not entirely clear why other than to throw verbal daggers at her son’s former companion.

"Andre wasn’t gay when he came to New York," Katherine declares. "He came to New York to be an actor."

Cal (Martin Burke), a well-off money manager, is now happily married to the much-younger Will (Nicholas Rodriguez), and the couple have a son, Bud (William May). And while we learn that Cal spent eight years mourning Andre before meeting Will, theirs is an idealized existence of upper-class comforts — one of many factors in McNally’s script that ultimately diminish its impact. Not everyone who emerged from or was affected by the AIDS crisis landed comfortably, after all.

All three of the adult characters remain uncomfortable as McNally rushes through a roster of topics, never fully illuminating any of them and resorting to a shallow display of verbal sparring between the homophobic Katherine and the too-nice Cal.

Learned brings the only true nuance to the show, skillfully unraveling the pain, grief and anger from behind Katherine’s stoic scotch-drinking public persona.

Burke is nevertheless skilled at side-stepping most of the treacle that’s embedded in Cal’s character. As Will, Rodriguez (best known of his role on the soap opera "One Life to Live") is rushed and tinny.

With its lack of real drama, "Mothers and Sons" veers into melodrama, more sensation than depth.