Tenshu, imprisoned and sentenced to death for murdering the men who raped his girlfriend, is sentenced to the electric chair. But he awakens to find that he hasn't been killed at all. He's given the option to volunteer in an experiment which may kill him. The experiment involves an alien virus type creature that transfers from person to person under intense anger - and they want the entity to switch to his body, as he does have a lot of anger. He's also put in a room with another death-row prisoner, a guy who is really crazy. The authorities put them together in the hopes that it'll provoke some violence. The entity is kept in the next room, currently in possession of a woman who happens to be one of the scientist's sister.
The entire movie takes place indoors, which gives it a claustrophobic feel, but he prison sets are well-designed and visually there's a lot to look at. There's also some nightmarish dream sequences with a lot of dead corpses and the last half-hour is when the special effects really get going.