On a snowy night, a stranger, his face swathed in bandages and his eyes obscured by dark goggles, takes a room at The Lion's Head Inn in the English village of Iping in Sussex. The man demands that he be left alone. Later, the innkeeper, Mr. Hall is sent by his wife to evict the stranger after he makes a huge mess in his room while doing research and falls behind on his rent. Angered, the stranger throws Mr. Hall down the stairs. Confronted by a policeman and some local villagers, he removes his bandages and goggles, revealing that he is invisible. Laughing maniacally, he takes off his clothes, making himself completely undetectable, and drives off his tormenters before fleeing into the countryside.
Sir Geoffrey Radcliffe (Vincent Price) is sentenced to death for the murder of his brother Michael, a crime he did not commit. Dr. Frank Griffin, the brother of the original invisible man (named John instead of Jack), injects the prisoner with an invisibility drug. As Radcliffe's execution nears, he suddenly vanishes from his cell. Detective Sampson (Cecil Kellaway) from the Scotland Yard guesses the truth while Radcliffe searches for the real murderer before the drug causes him to go insane.
The wealthy lawyer Dick Russell (John Howard (American actor)) funds the dotty old inventor Professor Gibbs (John Barrymore) to create an invisibility device. The first test subject for this machine is Kitty Carroll (Virginia Bruce), a department store model who had been fired from her previous job. The machine proves quite successful, and Kitty uses her invisible state to pay back her sadistic former boss, Mr. Growley (Charles Lane (actor)).
The grandson of Dr. Jack Griffin, the original Invisible Man, runs a print shop in Manhattan under the assumed name of Frank Raymond (Jon Hall (actor)). In his shop he is confronted by four armed men who reveal that they know his true identity. One of the men, Conrad Stauffer (Cedric Hardwicke), is a Gruppenführer of the Schutzstaffel, while a second, Baron Ikito (Peter Lorre), is Japanese. They offer to pay for the invisibility formula and threaten amputation if it is not revealed. Griffin manages to escape with the formula in his hands.
Robert Griffin (Jon Hall (actor)) is nothing but a mad, psychopathic killer who should be locked away for good. Still he manages to escape from the secluded Cape Town mental institution where he has been committed, and now he is looking for revenge on the respectable Herrick family. A family consisting of Sir Jasper and lady Irene, and their daughter Julie, who are engaged in entertaining, and inspecting, Julie's new boyfriend, newspaper journalist Mark Foster, in the family residence. Later that night Julie and Mark leave the residence together, and Sir Jasper and lady Irene are left alone. That's when Robert decides to pay the couple a visit. Quite unexpectedly he enters the residence and accuses the couple of leaving him to die out in the African wild, injured, when they were on a safari together. The Herrick couple defends themselves, claiming they were told that he was dead and not injured, but Robert doesn't buy their explanation. He demands they give him his share of the diamond fields they all discovered together on the safari. Jasper tries to tell Robert that the diamond fields were all lost in a series of bad investments.