Michael Learned (Katharine) and James Lloyd Reynolds (Cal) in Mothers and Sons at Philadelphia Theatre Company (photo by Mark Garvin)

“Sometimes – there’s God – so quickly!,” Tennessee Williams famously wrote.  Here, though, He doesn’t show up till 9:15.

Roughly 70 minutes into Terrence McNally’s 90-minute play, Mothers and Sons, principal character Katharine Gerard (played by Michael Learned, beloved star of The Waltons) opens up about the frustration and grief that have plagued her for years. Suddenly, there’s a ring of specificity and genuine feeling. Learned’s performance comes touchingly into focus, as do the others. It’s as if a veil has finally been lifted.

Till then, Mothers and Sons feels like the kind of shellacked, inert melodrama that populated Broadway in the 1940s – this, despite ostensibly being about a contemporary subject, AIDS, which is familiar McNally territory. In brief: Katharine, the mother of a man named Andre, who died of the disease in the 1990s, visits New York decades later to see Andre’s former lover, Cal, who has since married another man (Will), with whom he has a young son. Katharine has never forgiven Cal, Andre, the situation, or herself.

Mothers and Sons at Philadelphia Theatre Company (photo by Mark Garvin)

While there’s nothing really new here, there should be enough for a play. McNally’s approach to the subject of AIDS has always been less political than personal, and he’s good at sentimental portraiture.

Yet Mothers and Sons is primarily a vehicle for a celebrity actress of a certain age, who shows up in a Chanel suit and mink coat, slugs back a scotch, and proceeds to launch a series of bitchy one liners, proving to her fans that the old girl’s still got game. A thudding metaphor that drops early sets the over-obvious tone – it’s the shortest day of the year, you see, and Katharine is fretting: “It gets dark so quickly!” The whole thing looks similarly contrived, with actors entering and exiting to provide new scene groupings, and everybody (even the kid) is implausibly articulate and elegant. (McNally himself is an intelligent, cultured person, and he likes his audiences to know it.)

Neither Learned nor the other actors (James Lloyd Richards as Cal, Hugh Kennedy as Will, Patrick Gibbons, Jr. as the child, Bud) can completely overcome the script’s liabilities – but at least in the final moments, and there’s some actual art alongside the artifice. Ultimately, you may be touched by Mothers and Sons, as clearly many in the opening night audience were.

But you’re going to have to wait for it.

Through March 8, Philadelphia Theatre Co. at the Suzanne Roberts Theatre, 480 S. Broad St., (215) 985-0420. philadelphiatheatrecompany.org