It’s sort of a bummer when a movie’s big twist is not only known but becomes zeitgeist fodder way before you ever have the opportunity to watch it. Knowing the “secrets” of movies like Citizen Kane, Psycho, and The Crying Game didn’t necessarily ruin the movies for me, but I always wonder what it would have been like to experience them totally afresh. No movie exemplifies this better–and has become the stuff of memes and Simpsons bits–than Soylent Green does. It’s a movie I would argue most people ONLY know for the final twist, but should be remembered for a lot more.

The late ’60s and early ’70s were overpopulated with science fiction about protecting our environment, mistrusting authority, and being wary of unchecked expansion. Movies of this ilk that I’ve already covered in this column include Silent Running and Seconds, but other films like Planet of the Apes also fit. These sci-fi movies were didactic and angry and foresaw a quietly dystopian future where corruption wouldn’t be as clearcut as a single evil figure or regime. Systemic bad stuff leading to more bad stuff. These movies were cautionary tales, and Soylent Green might be the most cautionary of the bunch.

All right, let’s get it out of the way: Soylent Green is made out of people. It’s people! That’s a really silly line made even sillier by the uber-earnest shrieking of star Charlton Heston. This is literally the final shot of the movie, made bleaker than it might otherwise be in a vacuum by the picture painted in the build-up.

Soylent Green is based on the 1966 book Make Room! Make Room! by Harry Harrison and is set in 2022 (which seemed WAY further away in 1973 when the film was made) in New York City. The city has become totally overpopulated, with upwards of 40 million people clogging the streets, becoming a burden on the government to try to feed. Government-issued “soylent” (a portmanteau of “soy” and “lentil”) has become the main source of sustenance and the newest iteration, Soylent Green, is fast becoming the favorite. High protein, low carbs. “Don’t forget: Tuesday is Soylent Green Day.” The society has become a caste system, with the wealthiest people living in luxury in high-rise apartments and the poor living in hovels and sleeping on staircases; people in the middle-class have to jump over the poor to get to their own tiny flats.

Heston plays Detective Frank Thorn, who shares a slum apartment with a retired police analyst named Sol Roth (Edward G. Robinson). Thorn is tasked with investigating the murder of William Simonson (Joseph Cotton), a high-ranking member of the elite class. The strange part is, it appears that Simonson didn’t defend himself. Why would he resign himself to dying? Part of Thorn’s investigation leads him to Simonson’s live-in “companion” named Shirl (Leigh Taylor Young), basically a member of the concubine class, and Simonson’s bodyguard Tab Fielding (Chuck Connors). They’re off the hook because Simonson sent them out of the apartment at the time of the murder. But again, why?

Thorn gives Roth the classified Soylent Oceanographic Survey Report, 2015 to 2019 he’s found in Simonson’s apartment. Roth’s research reveals Simonson and the current governor of New York, Joseph Santini, were partners in a law firm, and that Simonson was also a member of the board of Soylent. Thorn decides the murder was an assassination and the culprit used a meathook instead of a gun to make it look like a robbery. Thorn goes to Fielding’s apartment to question him, but only finds Fielding’s concubine. He helps himself to a spoonful of strawberry jam from a jar on the table: an extravagance, as Roth surmises, far too expensive and decadent for a bodyguard and his companion to be able to afford. All signs point to something fishy going on with Soylent, and Thorn’s inability to drop the investigation, despite his superior’s order, makes him a target as well.

The movie unfolds like a great mystery, set in a sort of pre-apocalypse hellscape. A great amount of time is spent on how this fraught society is working. Food as we know it, is now considered a massive luxury, and one great scene involves Thorn and Roth eating a “feast” consisting of a piece of celery, a couple of cherries, and other such things that we consider staples. Roth even breaks down into tears when he sees a real piece of meat that they’re going to eat. We also learn about the concubine class, who live in luxury but are subject to the desire of just about every man they meet. Thorn uses Shirl for sex, but neither acts like it’s a big deal, and she allows him the use of her shower. She essentially just wants companionship, regardless of whose it is.

Naturally, the big sci-fi ideas here come from how the government and the police deal with the people in the city. There are too many of them and not nearly enough rations to go around. When Soylent Green runs out, there’s a riot, and the police use a machine they call a “scoop” crowd dispersal vehicle… which is just a bulldozer. People are lifted up into the huge machine’s front plow and others are crushed under the tires. There’s also an added encouragement for people to kill themselves, or, if they can afford it, go to a spa-like relaxation center where they are given drugs to die peacefully. Thorn follows a body at this establishment–while on the run from assassins–to disposal and processing, eventually learning that the dead are turned into the very thing the rest of the populace are given to eat. It’s still shocking, and presented in a music-free, documentary style which adds to the impact.

So, yes, “Soylent Green is people!” has become a punchline, but Soylent Green, and its hard-edged look at a world where the ecology, population, pollution, and everything else that makes the United States a first-world country, are totally obliterated–it is anything but a joke. While most post-apocalyptic movies now deal with zombies or gas shortages or other such wastelands, this was a movie made that forced its audience to look at how awful the world could be if we do nothing to stop it. The big reveal is just as big a gut punch now as it was at the time, and perhaps even more so. If you can watch the movie without waiting for the big, silly end line, then you’re in for a harrowing sci-fi parable indeed.

Images: MGM

Kyle Anderson is the Associate Editor for Nerdist. He writes the weekly look at weird or obscure films in Schlock & Awe. Follow him on Twitter!