Slater, Joe

(sometimes Slaader)  The Catskill man who, at the age of 42, was seized with strange visions of a nemesis who burns intensely, a creature of whose race Slater, in seizures, believed he himself belonged to.  During one such seizure he murdered
neighbor Peter Slader and was sent to the state psychopathic hospital in Albany, New York where, during an experiment by the narrator/intern, he died.

[Beyond the Walls of Sleep - H.P.L.]