By turns grandiose and silly, writer-director Richard Kelly’s “The Box” is an elaborate, paranoid science-fiction fable set in 1976 with a 21st century resonance.

What would you do if a very strange man showed up at your house and offered you a million dollars if you would push the button on a box you’ve mysteriously received, knowing that somewhere, someone you don’t know would die because of it?

That is the dilemma that faces Norma and Arthur Lewis (Cameron Diaz and James Marsden) whose bucolic existence with their nearly teenaged son Walter (Sam Oz Stone) is about to be destroyed when the strange Arlington Steward (Frank Langella), his face half-destroyed (an unconvincing digital effect), shows up with his loony proposition.

“The Box” is set in Langley, Va., headquarters of the CIA, and coincides with NASA’s first Viking mission to Mars.

Norma teaches English at a private school. Her class discusses Jean-Paul Sartre’s “No Exit,” whose moral - “Hell is other people seeing us as we truly are” - will reverberate as “The Box” ends.

Norma limps, the victim of an X-ray accident that burned off four of her toes (a situation inspired by Kelly’s mother).

Arthur is an optics engineer for NASA who hopes move into the astronaut program. (Kelly’s father was a NASA engineer at Langley.)

Once Norma impulsively pushes the button, what follows is never as frightening or disturbing as Kelly (of “Donnie Darko” and “Southland Tales”) intends.

This despite the fact that “The Box” has two of the most attractive people in movies at its center and several grandly conceived sequences.

Only as the story ends does Kelly bring home the point that the blithe push of a button to end a life has real-world consequences.

You can think of the West and its wars in the Middle East. You can think of drones that miss their targets and kill civilians.

But that doesn’t make “The Box,” adapted from Richard Matheson’s short story “Button, Button,” the kind of vital, mesmerizing sci-fi it aspires to be.

Rated PG-13. At AMC Loews Boston Common, Regal Fenway Stadium and suburban theaters.

(“The Box” contains disturbing themes, a couple of murders and lots of bloody noses.)