Two interpretations to it.
What is agreed on is that an eccentric scientist created a TV signal that when viewed, causes the formation of a deadly brain tumor in the viewer. The tumor alters their perceptions of reality, and makes them suggestible, so that they can be programmed as assassins, until they die.
The scientist and his peers then formed an organization that would broadcast this signal concealed in the worst order of pornography, snuff films, where someone is killed during the making of the film. Figuring that only absolute moral degenerates would watch it, then die of brain tumors.
However, the scientist himself went insane with a brain tumor, turned against the organization he helped create, and became convinced that the brain tumor was the next stage in human evolution, actually changing reality instead of just incorrectly interpreting it.
And this leads to the two interpretations of the movie. Either the rational view, that the brain tumors interfered with the perception of reality by the victim; or the science fiction view that the tumors *did* alter reality.
Makes a lot more sense now. Thanks!