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It's only as haunted as you are.
After two raids turn up zero evidence, narcotics detective Dwayne Spare infiltrates a crumbling apartment building where a suspected manufacturer of krokodil is hiding—but finds something much worse. The chemist Gerald Metzger isn't after money; he's lulling his most 'dedicated' customers into catatonia, to make contact with an eldritch being.
When Dwayne's cover is blown, he becomes Metzger's new test subject, an involuntary pilgrim into a world where "it's all just in your head" is far from a reassuring statement.