David Lowery's "A Ghost Story" is a thought experiment that requires viewers to meet it halfway — with the reward being a powerful musing on the pull of love over time.

It all happens in a house, one being rented by a young couple in love, known to us in the credits by the initials C (Casey Affleck) and M (Rooney Mara). Their marriage isn't perfect, though their squabbles — mostly about his resistance to her desire to move into a bigger house — don't seem unconquerable.

Then C dies in a car crash near their house, and M must go to the morgue to identify the body. After M leaves the morgue, C rises from the gurney and starts walking the long distance back to the house, which he then proceeds to haunt.

Lowery's conceit is that C haunts the house wearing a massive white sheet, with eyeholes that make him look like one of Charlie Brown's trick-or-treating friends. He moves slowly, silently, usually unnoticed by M, whom he watches grieving and getting on with her life.

One moment, C sees M saying goodnight to a guy after a date. The next moment, she's packing up boxes to move. New tenants move in, and the ghost stays. Time jumps, but the ghost remains fixed to this spot, waiting for M to return.

Lowery, as writer and director, has embarked on a true collaboration with Affleck and Mara, who starred in his 2013 Sundance Film Festival breakout "Ain't Them Bodies Saints." The actors are out there on the limb with the filmmaker, exploring through gesture and limited dialogue the emotions of loss, grief and longing felt by this widow and her not-too-departed husband.

Lowery stretches time to encompass the future and past, from ultramodern skyscrapers to Old West homesteaders. He invests the movie with images that are cosmic and poetic, with touches of Andrew Wyeth and Terrence Malick. And he makes room for intriguing side characters, including a ghost in a floral-print sheet waiting in the house next door and a loudmouthed partygoer (Will Oldham) who annoys a group of drunken party guests with his musings on the futility of life.

But the core of "A Ghost Story" is the byplay between Affleck and Mara, both fully committed to Lowery's offbeat but resonant vision. Even when they can't communicate with each other, the way each occupies their space in this house speaks volumes.

* * * 1/2

’A Ghost Story’

A minimalist supernatural story of a ghost (Casey Affleck) and the woman (Rooney Mara) he once loved.

Where • Broadway Centre Cinemas.

When • Opens Friday, July 28

Rating • R for brief language and a disturbing image.

Running time • 92 minutes
This image released by the Sundance Institute shows Rooney Mara, left, and Casey Affleck in a scene from
This image released by the Sundance Institute shows Rooney Mara, left, and Casey Affleck in a scene from "A Ghost Story," by filmmaker David Lowery, an official selection of the NEXT program at the 2017 Sundance Film Festival. The film reunites co-stars Mara and Affleck, who starred as outlaw lovers in “Ain’t Them Bodies Saints." (Andrew Droz Palermo/Sundance Institute via AP)