A mad scientist name Anton Lupesky invents a drug that can free the soul of the user and allow them to posses the bodies of corpses. The horrible side effect is sometimes fatal hallucinations that leave the survivors incurably mad.
A crazy scientist called Anton Lupesky develops a drug called Anphorium, which makes the soul leaves the body and enters in any corpse with eyes. It affects the nerve center, causing madness as side effect.