A contrived spook film shows two scientists experimenting with phosphorus, with the aim of illuminating internal organs as an aid in operations. The experiment gets mixed up, and a serum from the West Indies, developed from cats, gets injected into one of the scientists, turning him into a
killer with cat paws. The other scientist believes the experiments must stop, but the scientist injected with the serum disagrees and kills his colleague. Several people are clawed to death before the cat-killer scientist is stopped.