When Seth Brundle makes a huge scientific and technological breakthrough in teleportation, he decides to test it on himself. Unbeknownst to him, a common housefly manages to get inside the device and the two become one.

A rogue scientist near a small desert town arouses the suspicion of the town's doctor when his lab assistant is found dead from a case of acromegaly, which took only four days to develop. As the doctor investigates, aided by the scientist's new female assistant, they discover that something is devouring local cattle and humans in increasingly large quantities.

Industrialist François Delambre is called late at night by his sister-in-law, Helene Delambre, who tells him that she has just killed her husband, André. Reluctant at first, she eventually explains to the police that André invented a matter transportation apparatus and, while experimenting on himself, a fly entered the chamber during the matter transference.

Fifteen years after his father's experiments with matter transmission fail, Philippe Delambre and his uncle François attempt to create a matter transmission device on their own. However, their experiments have disastrous results, turning Philippe into a horrible half-man, half-fly creature.

Prof. Erling and his financial backer Victor build a prototype time machine to snatch objects from the past. Latest find, a statuette, radiometrically dates to 5200 AD! When this draws colleague Richard Hedges to the island lab, Erling reveals that 20th-century objects put in the machine seem to be "traded" for analogous future objects by intelligent life. And on the sly, Victor's been trying to get a living visitor. Does the future need help, or is the present in danger?