You need to watch the scariest sci-fi masterpiece on Amazon Prime ASAP

In 1963, Don Chaffey’s Jason and The Argonauts was released. A mythological movie about ancient Greece starring Todd Armstrong as Jason and Nancy Kovack as Medea, the movie isn’t remembered for Chaffey or either of the leads. Instead, Jason and The Argonauts was a showcase for the stop-motion animation of Ray Harryhausen.

Before computers and CGI, Harryhausen was one of the most prominent special effects masters. His work on Jason, like its army of skeleton warriors, became iconic. Among those wowed was a young Chris Walas sitting in one of Chicago’s grandest old movie houses, the Gateway Theater. Jason was the first movie Walas ever saw on the big screen, and it changed his life. He told Terror Time in 2016 he knew he wanted to work in movies and somehow become part of “creating that same kind of unimaginable magic.”

Walas was able to reach Harryhausen’s heights when working with David Cronenberg on the 1986 movie The Fly. A better movie than Jason, The Fly is nonetheless defined by its jaw-dropping special effects, which can produce a strong reaction in viewers even 36 years later.

Cronenberg’s first trick in The Fly is to spend the front half of the movie establishing the sexual magnetism of Seth Brundle (Jeff Goldblum). Almost played by John Lithgow, who backed out due to the movie’s inherent grossness, it’s hard to imagine Brundle played by anyone else. Goldblum brings the scientific curiosity he’d become more famous for in blockbusters like Jurassic Park and Independence Day, a perpetually excited nerd with perfect abs.

It’s not very hard for him to convince journalist Veronica "Ronnie" Quaife (Geena Davis) to ditch a party to come with him, especially when he promises to show her something that will change humanity. When he takes her to a lab that appears to be in a basement apartment, she blanches. But when he promises her that it’s cleaner on the inside, she follows him for a seductive scientific demonstration.

Brundle plays her a little piano before it’s on to the main event, his telepods, two black devices with ridges that Ronnie refers to as telephone booths. But she’s willing to play along, and when Brundle asks for a personal item to showcase what they can do, she flirtatiously gives him one of her stockings. A little ruffled, Brundle is able to show what’s possible: Teleportation. But when he realizes that she wants to write about the discovery, he freaks out and she leaves.

Ronnie works for a science magazine called Particle that’s run by her ex-boyfriend, Stathis Borans (John Getz). Cronenberg doesn’t have much positive to say about journalism in The Fly, considering that Ronnie has slept with one boss and soon starts sleeping with the subject of her reporting. While this is a frustrating cliché in movies featuring female journalists, Cronenberg isn’t truly interested in media in The Fly. He’s interested in... well, you’ll see.

Borans blows off Brundle as a hoax, which couldn’t make him happier. Over cheeseburgers, Brundle convinces Ronnie to take her time reporting out the story. Instead of an article, how about a whole book on his process of solving living transportation? Right now, his machines can only teleport inanimate matter. He asks for a year.

They start their work together inauspiciously, accidentally destroying animals by turning their skin inside out. However, with Ronnie’s help, Brundle uses steaks to realize that his pods are creating synthetic versions of biological material, not the real thing. They make a few adjustments, and soon a baboon is able to pass through unharmed. While any movie on the subject of teleportation couldn’t exactly use real science, Cronenberg appears especially uninterested in how, exactly, Brundle is doing what he’s doing. He’s much more interested in when he makes mistakes.

A love triangle emerges, and a distraught Brundle gets hammered and decides to test his machine himself. However, in his drunken rage he misses one crucial element: The fly inside the telepod with him.

At first, the changes to Brundle’s body are euphoric. He’s impossibly strong and seized by a spirituality regarding the process. The machine has purified his body, he tells Ronnie, removing all signs of weakness and doubt. However, Ronnie becomes concerned about the odd injury on his back, where inhuman hairs seem to be developing. She also worries when Brundle keeps insisting on having her experience teleportation too.

Eventually she leaves him, prompting Brundle to try to get another woman he meets at a bar (Joy Bushel) to go through the process. He shows off his strength, breaking one of her friend’s arms when they arm wrestle, but she has no interest in the machine. Ronnie intervenes just before Brundle can force the woman inside.

Ronnie insists that Brundle has changed. All he can eat is sugary foods, and he becomes increasingly hostile to anyone around him. He throws Ronnie out, but once his fingernails start falling out, it’s hard for him to deny the problem.

Brundle’s transformation, made possible by the work of Walas and his team, is one of the most stunning in cinematic history. It’s gross, full of mucus, vomit, and half-formed heads. But every prop has a point, and Brundle reveals the horror that he had in him all along.

The Fly is streaming on Amazon Prime.