Robert Griffin was a man who knew of some heretofore untapped diamond mines deep in the wilds of Africa. How he came about this information is unclear, although it is known he shared it with his friends Jasper and Irene Herrick, whose daughter Julie he planned to one day court. The three each signed a document saying each would get an equal share in whatever profits were reaped from the mine. On the trip to find the mines however, Robert was struck by a falling tree branch and knocked unconscious. The Herricks went on without him, although they left one of their bearers with him. After Robert did not regain consciousness, the bearer caught up to the Herricks' party and informed them that Robert had died.
Robert survived, however, but had lost his memory as a result of the blow to the head. Finding his way back to England he landed a job as a dockworker, until he was hit on the head again, this time by a crane, which caused him to regain his memories. It also, apparently, caused him to develop psychotic tendencies, because not long afterwards he was admitted to an insane asylum after committing multiple murders. He had become extremely paranoid and would turn violent whenever he so much as thought someone was spying on him or otherwise out to get him. Presumably all of the murders were the result of total misunderstandings on Robert's part. Eventually, after killing two nurses and a doctor, Robert escaped from the asylum and found his way to where the Herricks had made their home.
Polite at first, he soon turned angry and violent when told that Jasper had lost what would have been his share in bad investments. Determined to get what he felt he deserved Robert revealed he'd kept the document they all signed. It had been in his pocket ever since that day in the jungle when he was left for dead. Realizing he could use this to destroy them, Irene spiked Robert's drink, and then she and Jasper stole the document and dropped him off out in the middle of nowhere, where he fell into the river and almost drowned. He was rescued, however, by a neighbor of the Herricks, Herbert Higgins. Higgins believed his story and helped him hire a lawyer, Jim Feeney, but Feeney quickly realized they had no case without the document, which the Herricks had almost certainly destroyed.
At his wit's end, Robert ran away and wound up seeking shelter at the home of Dr. Peter Drury, a scientist who was experimenting in making things invisible. He had already succeeded with animals, including his faithful dog Brutus, but he needed a human test subject. Robert volunteered, and the experiment was a complete success. Although Drury wanted Robert to remain with him for further study, Robert had other ideas and escaped. Finding his way back, he first repaid Higgins for helping him by helping win a lot of money in a dart game, then he paid the Herricks a visit and strongarmed Jasper into agreeing to give him their entire estate and promise to let him court Julie.
Jasper agreed but pointed out that none of this would do Robert any good as long as he was invisible, so Robert returned to Drury's home and watched the scientist restore Brutus to visibility by giving him a blood transfusion - which cost the doner dog his life. Now completely insane, Robert killed Drury and used his blood for his own transfusion and became visible again, burning down Drury's house and taking the transfusion equipment with him. Brutus escaped, however. After that, Robert, under the alias Martin Field, lorded over the Herrick household, allowing his friend Higgins to come and go as he pleased, to the chagrin of Julie's boyfriend Mark Foster, whom Robert instantly disliked and decided he had to get rid of.
The only thorn in his side was Brutus who constantly (and literally) hound him. Knowing that the dog wanted revenge for him killing its owner, a worried Robert told Higgins to get rid of the animal. Afterwards effects of the transfusion began to wear off and, needing more blood, Robert lured Mark into the basement and knocked him unconscious and began attempting to take his blood. In the meantime, Sir Frederick Travers, investigating Dr. Drury's death, followed the clues to the Herrick household. He and Jasper quickly realized what Robert was up to, and burst in on Robert before he could finish the transfusion, saving Mark and leaving Robert only partially visible. Robert's attempt to escape was thwarted by Brutus. Higgins' efforts to get rid of him had failed, and the vengeful dog killed the man who had murdered his beloved owner.
Despite his last name, Robert Griffin is apparently not related to the more famous Jack Griffin and his family.