Act I
A crime scene in a strange laboratory: Veronica Quaife tells her story to a police officer. In flashback, Veronica attends a reception sponsored by Particle Magazine, a scientific journal for which she writes. There, she meets Seth Brundle, a deeply eccentric scientist - either madman or genius - who claims to be working on an invention that will "change the world as we know it." Though skeptical, she follows him back to his laboratory, where she witnesses a demonstration of the teleportation pods which are his life's work: he transports her stockings from one pod to the other.

Shocked to discover that she is a reporter for a science journal, Brundle tries to talk her out of writing about his discovery, to no avail. She takes the story to her editor and ex-lover, Stathis Borans, who dismisses Brundle's feat as a trick. Brundle shows up at Veronica's office and they strike a deal: she will hold off writing an article in order to document his research for a future book. Consulting with scientists, Stathis learns that Brundle is a legendary genius. Suddenly, Veronica's scoop seems a lot more interesting to him.

Brundle tries to transport a baboon, but his machines turn the animal literally inside out. Though his telepods work on inanimate objects, they are still incapable of transporting living things; they have not learned to understand the flesh. When he and Veronica fall into an affair, Brundle discovers new appreciation for the flesh, which he begins to teach to his computers. Soon, he makes his first successful teleportation of a baboon. Forced to deal with Stathis' jealousy, Veronica can't make Brundle's celebration. Drunk and angry, Brundle attempts his ultimate feat alone: to teleport himself. A fly buzzes around one of the pods as he enters it. The experiment succeeds: Brundle emerges from the other pod whole. The New Flesh has come.

Act II
Veronica continues to tell her story to the officer: when she returns to the laboratory, Brundle elatedly reports on his teleportation. He seems oddly changed, however: frenetic, physically powerful, his appetites insatiable, including for sex. She also finds strange-looking hairs growing on his back. With Messianic fervor, Brundle insists that Veronica go through the telepods, so her flesh can be purified like his. When she refuses, he abandons her and heads to a dive bar, where he arm-wrestles a cowboy, Marky, for the right to take his girlfriend, Tawny, home. Veronica takes the hairs from Brundle's back to a lab for analysis. She learns that they came from a fly. Brundle spends the night with Tawny, and then tries to force her through the telepods. Veronica interrupts them: "Be afraid. Be very afraid." Veronica tells him something went terribly wrong during his teleportation. Brundle rejects her claims as jealousy, and tosses her out of his lab.

Over the next few weeks, Brundle's body starts to deteriorate. Fearing that he is dying, he asks the computer for answers: a fly had entered the telepod during his teleportation, which fused his DNA with that of the insect. Veronica receives a phone call from Brundle, imploring "help me." She returns to his lab to find him grotesquely transformed, his human body changing into that of a fly. A distraught Veronica takes Stathis to Brundle's lab while he's sleeping. She tells Stathis she is pregnant with Brundle's baby, and had a dream where she gave birth to a giant maggot. Stathis says he will arrange for her to have an abortion.

When Veronica returns to the lab, Brundle warns her that as he continues to transform into a fly, he will be increasingly unable to protect her from himself. Stathis takes Veronica to abort the fetus. Brundle bursts in and carries her off. Now more fly than ever, he will not allow anyone to destroy his offspring. Brundle plans to fuse the DNA of Veronica and the fetus with his own. He forces her into one pod, gets into another, and commences the teleportation sequence.

Entering with a gun, Stathis frees Veronica, who tries to stop the computers. Instead, their efforts confuse the equipment, which turns Brundle inside out, as it did the baboon. Grabbing Stathis' gun, Veronica puts an end to her lover's suffering. Veronica finishes telling the officer her story. She has made a decision: she will not allow Brundle to die completely, and will bear his child into the world. The New Flesh has come.

Synopsis by David Henry Hwang