The main character in “Post Mortem” has a movie job that hasn’t been used as a plot device before, as far as I know: He transcribes the coroner’s reports during autopsies.

Tough gig. And, as “Post Mortem” unfolds, we see that this job suits the grim character, and also that it puts him in a position to witness a unique moment of Chilean history.

The man’s name is Mario, and he is played by Alfredo Castro, the beaked-nose actor who starred in director Pablo Larrain’s previous film, “Tony Manero.” That film was about an antisocial man obsessed with the John Travolta character from “Saturday Night Live,” to the exclusion of any other human dimension.

Mario in “Port Mortem” is nearly as strange. He has a voyeuristic interest in a neighbor (Antonia Zegers) with whom he eventually establishes contact. Her building is a gathering place for political activists, and because this is Santiago, Chile, in 1973, the year Salvador Allende was overthrown in a coup and Augusto Pinochet began his dictatorship, such gatherings are very dangerous.

The coup happens in the course of the movie, but only as a slightly surreal upheaval that destabilizes Mario’s peculiar life. He stalks through the film in a funk, peering out his window or blandly transcribing his mortuary details.

At one point, a very significant corpse is brought to the attention of the team at the morgue, an event that barely causes a ripple in Mario’s demeanor. But the violence of the streets can’t stay outside his life forever.

While “Tony Manero” was a challenging but mostly accessible movie, “Post Mortem” is primarily challenging. Even Larrain’s style is unnerving, a widescreen approach that gives you the odd feeling that information is being left out of the top and bottom of your vision, as though you were looking through lateral slats in a window.

Nevertheless, the film has a powerful subject and a distinctive lead actor. The final sequence is the opposite of comforting, and offers no exit whatsoever.

Not for the faint of heart. But we’ll be hearing from this director again: Larrain’s new film “No” has been getting raves at the current Cannes Film Festival and just got picked up by Sony Pictures Classics, so it stands a chance at being his first film to get big-time international distribution.

“Post Mortem” (3 stars)

An unnerving film set during the Chilean coup in 1973, seen through the skewed perspective of a zombielike mortuary employee. Director Alfredo Castro doesn’t do anything the easy way, but by the time you get to the excruciating ending of this movie, you see what the design was. In Spanish, with English subtitles.

Rating: Not rated; probably R for nudity, subject matter.

Showing: Grand Illusion theater.