The Invisible Man’s Revenge

Robert Griffin murders two orderlies and makes a daring escape from the Cape Town mental institution. He reveals his intent to seek revenge against the Herrick family. The escape sets him on a path toward reclaiming what he believes is his.

Sir Jasper and Lady Irene Herrick greet Julie's new boyfriend, Mark Foster, at the family residence. Later, Julie and Mark depart, leaving the couple alone with Robert. He confronts them, accuses them of abandoning him, and tries to force a deal, even suggesting Julie's hand in marriage; Lady Irene drugs him and he passes out.

The Herricks seize the written partnership agreement and throw Robert out of the house. He nearly drowns while unconscious, but Herbert Higgins rescues him from the water. The incident marks the start of Herbert's involvement in Robert's revenge plan.

Herbert tries to blackmail the Herricks with the information Robert provided. The local chief constable Sir Frederick Travers declares Robert's claims void and orders him to leave the jurisdiction. Robert departs for London, stepping into a new phase of his plan.

On his way to London, Robert encounters the eccentric scientist Dr. Peter Drury who is eager to test an invisibility formula on him. Robert agrees to become Drury's subject, seeing a path to revenge. The meeting plants the seed for his future transformation.

Drury demonstrates the transformation by restoring visibility to his dog Brutus after a transfusion. Jasper privately agrees to marry Julie to Robert if he regains his visibility, tying the outcome to Robert's newfound power.

Robert returns to Drury's laboratory, knocks Drury unconscious, and uses a transfusion of Drury's blood to make himself visible again. Drury dies as a result, and Robert sets the laboratory on fire to avoid capture and escapes.

With a new identity as Martin Field, Robert moves into the Herrick estate as the owner and begins living there again with the family. He asserts control over the property and plans his next moves from within the house.

Herbert learns of Robert's return and makes a second attempt to blackmail him. Robert pays Herbert 1,000 pounds to go away, but imposes one grim condition: Herbert must kill Brutus.

At breakfast, Robert notices his invisibility slipping away. He lures Mark into the wine cellar and begins another transfusion using Mark's blood to maintain his power.

Travers arrives at the estate, aided by Herbert and Jasper, and they break into the cellar just as the transfusion is about to finish. They intervene and save Mark's life.

In the final confrontation, Brutus the dog attacks Robert and kills him, ending the vengeful plot. The Herrick family survives the ordeal intact, though forever marked by the events.