Geoffrey Radcliffe, the brother of the Invisible Man, is scheduled to be hanged for the murder of his brother. After a visit from his friend Dr. Frank Griffin, he mysteriously disappears from prison. Inspector Sampson realizes that Griffin is the brother of the original Invisible Man and has given Geoffrey the formula to aid his escape. Can Geoffrey elude the police dragnet and track down the real murderer? More importantly, can Griffin discover an antidote before the invisibility formula drives Geoffrey insane?