Substance D Is The Most Dangerous Drug Ever. Undercover Narcotics Agent Fred, Assumes The Identity Of Drug Dealing And Using Bob Arctor. Unfortunately Substance D Destroys The Links Between The Brain's Two Hemispheres, Leading To Disorentation And Then Complete And Irreversible Brain Damage. Philip K. Dick ; [cover Design By Heidi North]. Originally Published: Doubleday & Co : New York, 1977.