The Invisible Man's Revenge
An eager scientist (John Carradine) tests his new formula for invisibility on an escaped fugitive (Jon Hall). When the formula works the criminal runs off to terrorize a family he believes cheated him out of a fortune years earlier.
Robert Griffin (Jon Hall) 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.
Robert refuses to give in, threatening to sue the Herricks, and to calm him down and get him off their backs they offer him a share in an estate, the Shortlands. His counter-proposal is that they should arrange for him to be married to their daughter Julie. After saying this he is drugged by Lady Irene and passes out in their home. The Herricks realize that their old friend and companion has gone completely mad, and while they are frightened of what he could do to them if they don't comply to his wish they see no problem with stealing the agreement made or pushing him further along the path of insanity with their betrayal. They search Robert's clothes and finds the written partnership agreement they all entered into some time ago. Taking the paper they next callously throw Robert out of their house. Robert nearly drowns where he lies, unconscious, but is saved by a local Cockney cobbler by the name of Herbert Higgins (Leon Errol).
Herbert decides to use this new found possibility - the information he got from Robert - to blackmail the Herricks. He is unsuccessful, as Jasper calls on chief constable Sir Frederick Travers (Leyland Hodgson). The chief constable declares Robert's claims to the Herricks' estate as void and orders him to leave his jurisdiction. Robert leaves for London, but on his way he happens to come by the home of eager scientist Dr. Peter Drury (John Carradine). This scientist is involved in some questionable research, and is very eager to find a suitable subject to test his new experimental formula on - a formula for invisibility. Robert asks that the doctor try it on him, and he agrees, completely in the dark of the fact that Robert wants to use this to get his revenge on the Herricks. Robert forces Jasper to sign over their entire estate to him. He also finds time to help his saviour Herbert to win a game of darts at the local inn.
Jasper secretly also agrees to give his daughter's hand in marriage to Robert - if he ever regains his visibility. Robert goes back to the scientists laboratory and witnesses how the doctor restores visibility to his dog Brutus, by giving him a blood transfusion. Robert breaks into the laboratory and knocks the doctor unconscious, before performing a blood transfusion on himself, using the doctor's blood. The transfusion results in the doctor's death, and to avoid capture Robert sets the laboratory on fire and takes off just before the police arrive on the scene.
Robert changes his identity to "Martin Field" and moves in with the Herricks at the estate which he is now owner to. When Herbert finds out about Robert's return he makes a futile attempt to blackmail him too, and out of pity - and perhaps thankfulness - Robert pays the man a 1000 pounds to get rid of him. Robert has one condition for paying the money: that Herbert kills the doctor's dog Brutus, who has followed Robert back to the Herrick estate after the fire.
Robert starts losing his visibility one day at the breakfast table, with Julie and her fiancé Mark present. He tricks Mark to follow him down into the wine cellar, where he knocks the man out, starting another, second blood transfusion with Mark's blood.
Chief constable Travers arrives at the estate after he has found out about Robert's return. With some help from Herbert and Jasper they break into the cellar just as the transfusion is about to be completed, in time to save Mark's life. Robert is attacked by the still very much alive Brutus, and killed. Mark tells the others that Griffin went insane when he was locked up in the asylum, and meant no one any harm until he escaped.
good versus evil, revenge, murder