The Fly follows Seth Brundle, a brilliant and eccentric scientist working on teleportation technology. At a press event he meets up with Veronica Quaife, an investigative journalist looking for her big scoop. They go back to his apartment and lab where he shows her what he's been working on. Brundle gives a demonstration of his Teleportation Pods by transporting Quaife's pantyhose from one pod to another. After Quaife reveals her tape recorder to get quotes for an article Brundle reacts poorly and demands that she does not go public with what she just saw. He explains that the Teleportation Pods are not ready and that they can only transport inanimate objects at the moment. He explains that the computer can't handle flesh and that it gets confused. She agrees to keep it quiet for now in exchange for exclusive rights to the project. After she leaves she does reveal her recordings to her editor and ex, Stathis Borans who dismisses it as a hoax.
Quaife returns to Brundle's apartment and he demonstrates the Pods inability to transport living creatures by attempting to transport a baboon. The baboon arrives in the second Pod turned inside out. After a night a romance Brundle is inspired to make alterations to the system to account for "the flesh". He retries on a second baboon and the experiment is successful with the baboon being transported safely. After a night of celebration and a bit too much champagne, Brundle decides to test the Pods on himself. During the experiment unbeknownst to Brundle a house fly enters his pod. He is transported successfully and emerges seemingly unaltered. He meets again with Quaife and demonstrates a new found sense of acrobatics and stamina that he attributes to the transportation process purifying him. However after a while Quaife begins to become concerned with his increasingly erratic behavior, consumption of sugar, and hairs growing from a wound in his back. Brundle insists nothing is wrong and even tries to force Quaife to enter the Pods and to go through the transportation herself. She manages to fight him off and Brundle throws her out and leaves for a bar. Inside he challenges a bar patron to an arm wrestling match and leaves the man with a compound fracture. He brings home Tawny a woman from the bar and tries to force her to go through the teleportation process as well. Quaife comes back and rescues the woman. Brundle throws them both out and after a fingernail falls off he begins to realize something went wrong with the transportation.
The now decaying Brundle consults the computer to find out what is happening to him. He discovers that the fly had entered his Pod and the computer, unable to differentiate between the two living creatures, had merged them both at a molecular-genetic level. Brundle begins to deteriorate at an alarming level losing hair, losing body parts, and growing skin lesions. He realizes he can no longer eat normally and has to vomit digestive enzymes in order to consume food. He also gains the ability to walk on walls and stick to things. He reveals to Quaife that he is becoming a hybrid he refers to as Brundlefly and that he is losing control of his impulses. He begins to develop a fusion program for the Teleportation Pods to combine himself with another human to gain back his humanity. Quaife discovers she is pregnant with Brundle's child and reveals this to Borans. She is determined to have the pregnancy aborted after a nightmare in which she gives birth to a maggot. Borans takes Quaife to the clinic but while waiting Brundle comes and kidnaps Quaife. He begs her to keep the child believing it to be his last chance at humanity. He tells her that he developed the fusion program and is going to fuse her, her unborn child, and himself together to eliminate the fly.
Borans breaks into the lab with a shotgun in an attempt to rescue Quaife, however Brundle (now no longer human but fully fly) discovers him and melts his hand and ankle with the digestive enzymes. Brundle forces Quaife into one of the Teleportation Pods and enters the second one himself to start the process. An injured Borans manages to shoot the Pod containing Quaife freeing her. Brundle attempts to exit his pod but the process begins and he is transported into the third pod. Inside the third Pod the computer had fused the Brundlefly with the wires and door of the other Pod. Brundle begs Quaife to kill him to put him out of his misery and she obliges.
While there is some gore in the movie most of it is downplayed. The gore that is there is meant to horrify and shock rather than to make you gag or feel sick. The horror itself therefore mostly comes from the performance given by Jeff Goldblum and cast as well as from the plot itself. The movie begins with a sense of wonder and optimism only to spiral downward to an inevitable depressing conclusion. That's the kind of horror that stays with you long after the movie is over and the kind that works. The viewer feels trapped in the story watching like a fly on the wall as the experiment goes awry and Brundle slowly transforms with no escape. It's an uneasy and unsettling feeling.
The only drawbacks to the movie are the pacing and the character of Stathis Borans. The transformation, which should have felt long, slow, and deliberate, feels rushed. The actual experiment doesn't happen until almost halfway through the movie and the actual final Fly form is only seen at the very end for a few moments. Now there's definitely a line, the Fly could have been shown too much and become corny but the movie goes in the opposite direction and barely shows it at all. I would have loved to have seen more of Brundle's transformation if only to give Jeff Goldblum even more time to stretch his wings out. The Fly is only an hour and a half when it easily could have sustained an additional fifteen to thirty minutes without feeling like it was dragging on. As far as the character of Stathis Borans, he feels unnecessary. Removing him from the story completely and reworking it would have been a better idea. The original draft for the movie had him as a different character, a friend to Brundle which I think would have worked better. There was no need for the romance backstory.
The Fly is a tightly crafted, well written, and well acted cinematic masterpiece. It could have used a bit of room to stretch out but overall a minor complaint for a otherwise superb movie. Horror movies would do well to use The Fly as an example on how to shock your audience without overly relying on jump scares or gore. It's just the right amount of grotesque body horror and exploring the horror of the human psyche.