Substance D is an addictive illicit substance in the book A Scanner Darkly by Philip K. Dick.

It evertually causes brain damage resulting in a split brain, lots of mental problems, and being really burnt for the rest of your life.

Treatment is offered at New Path.

Substance D is basically methamphetamine. Philip K. Dick was living in a houseful of speed-freaks during the period he was writing about in A Scanner Darkly.

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