This sequel to The Fly (1958) sees the original scientist's son reconstructing the matter transporter which turned his father into an insect, with the young man's experiments leading him down the same insectoid path. Remember that scientist that was trying to perfect a matter transportation machine but got fused with a fly when one of the little critters got into the transporter with him? Well, this story is about three of his descendents (a son, Henri Delambre, played by Brian Donlevy and two grandsons). Seems the son wants to continue and perfect the machine while his two sons want to get out of the scientist business and live "normal" lives. The oldest son, Martin, decides to take a wife (who just happens to have escaped from a mental hospital after her parents died). Martin's father is not happy with this intrusion but finally gives in because he understands him son's needs. They all try to be a happy family until humans used in botched experiments are discovered by the new bride and the police nearly discover the lab while looking for Martin's wife. Everyone tries to get out of there via the transporter but things just don't go according to plan .