John Croxley was a civilian who was possessed of the power of extra-sensory perception of the "telepathy" type, which enabled him to read the minds of other people. He regarded this power as a curse, and sought medical aid for it.
Me was married up to and including the time of "E.S.P.," but his wife, named Stella, was killed in the course of that instalment when, the course of a dogfight with a UFO, S.H.A.D.O. Colonel Paul Foster sent it into Croxley's house, which caused it to crash-land and destroyed it, killing Stella Croxley. Blaming Foster for Stella's death, the grief-stricken Croxley used his powers to read Foster's mind. From this, he was able to learn all about the S.H.A.D.O., which he intended to destroy. (Croxley never found out that the aliens against whom the S.H.A.D.O. was charged with defending Earth had actually granted him his power specifically to destroy the S.H.A.D.O.)
Writing a screenplay which contained a detailed description of all the S.H.A.D.O.'s operations, Croxley sent it to Harlington-Straker Film Studios, the front for the S.H.A.D.O. The S.H.A.D.O.'s Commander, Edward Straker, was horrified at what he read in the script's contents, since the secrecy surrounding the very existence of the S.H.A.D.O. itself had to be kept maintained at all costs because of the potential planet-shattering implications, as Foster himself had pointed out in "Exposed."
Confronted, Croxley eventually had to be shot in the back to prevent him from assassinating Straker. In S.H.A.D.O. Headquarters, Straker fed the only copy of the screenplay of whose existence he personally knew into an incineration chute in his office, thereby burning it unproduced. Whether Croxley had made any other copies of the screenplay he had written, and whether any other such copies still existed, was never revealed in the instalment.