An intern in a mental hospital relates his experience with Joe Slater, an inmate who died at the facility a few weeks after being confined as a criminally insane murderer. During the third night of his confinement, Slater has the first of his "attacks". He bursts from an uneasy sleep into a frenzy so violent it takes four orderlies to strait-jacket him. For nearly fifteen minutes he gives vent to an incredible rant. As an undergraduate, the intern had built but never tested a device for two-way telepathic communication. The device was designed around his principle that thought was ultimately a form of radiant energy. Heedless of any ethics, he attaches himself with Slater to the device as Slater lies near death. With the device switched on, he receives a message from a being of light whose experiences had been what were transmitted through the medium of Joe Slater.