Milton Robinson is a good man living a sad life in a small Pennsylvania town. A widower, he has no visitors, save for his daughter, who checks on him with a performative worry.

Played bySir Ben Kingsleywith a bland American accent and a meek timidity, Milton never misses the weekly town halls, where citizens can speak directly to city officials. He always has a list of complaints, but one gets the feeling Milton is less interested in effecting change in his community than having somebody listen to him.

So it’s no wonder that when an alien crash-lands in his backyard, he doesn’t freak out, but instead invites the little fellow in. Finally, someone to connect with, even if the crash killed his prized azaleas and crushed his birdbath.

Marc Turtletaub’s gentle, winning comedy “Jules” is technically a science-fiction film, but it is actually about loneliness and aging, much like the classic ’80s audience-pleaser “Cocoon,” which this film often resembles. In that Ron Howard film, aliens provide a fountain of youth at a senior living center that had 77-year-old Don Ameche breakdancing. Spoiler alert: Kingsley doesn’t dance. Instead, Milton and two elderly women, Sandy (Harriet Sansom Harris) and Joyce (Jane Curtin) play nursemaid to the injured alien, whom they call Jules (Jade Quon).

Keeping Jules a secret means avoiding his daughter Denise, played by Santa Cruz native Zoë Winters (“Succession”), who thinks he’s becoming delusional.

Turtletaub, working from an original script by Gavin Steckler, isn’t interested in regeneration, but reawakening. “Jules,” which made its world premiere at theSonoma International Film Festival, is a plea for seniors to find joy and illumination in their final years.

That’s a tall order, given this trio’s dug-in eccentricities. But Jules acts as a one-entity senior citizen outreach center. The alien never speaks, but observes his benefactors with passive bewilderment. Quon, a Hollywood stuntwoman wearing a prosthetic suit, turns in an astonishingly moving silent performance.

Naturally, there are the required plot elements of the science-fiction genre, such as standard issue subplot of government agents attempting to locate the alien, and some interesting superpowers Jules reveals late in the movie.

But the film’s pleasures are the three cantankerous curmudgeons. Of course there’s Kingsley, whose introverted, mumbling Milton is the polar opposite of Salvador Dalí, whom he played earlier this year in“Dalíland.”

Sansom Harris, a skilled comic actress who had recurring roles in the TV series “Frasier” and “Desperate Housewives,” as well as a hilarious cameo as a talent agent in the Paul Thomas Anderson film“Licorice Pizza,”has her best film role as the skittish Sandy.

Curtin got her start, of course, on“Saturday Night Live”and starred in two classic sitcoms, “Kate & Allie” and “3rd Rock From the Sun.” But it wasn’t until “Jules” that she got to belt out a cover of Lynyrd Skynyrd’s “Free Bird.”

All three are 68 or above, and this is their time. Several successful films of late have featured older actors in lead roles, from best picture winner“一切都在一次”to“80 for Brady.”No alien superpowers needed.

Reach G. Allen Johnson:ajohnson@sfchronicle.com