The Red Right Hand — Joel Townsley Rogers

Dr. Harry Riddle's first problem was the whereabouts of the grotesque hitchhiker who had vanished after killing Innis St. Erme. The second was what he did with St. Erme's missing right hand. Over the course of one nightmarish day, more victims turn up in the killer's wake. But in this hallucinatory mystery, the clues lead Riddle to doubt his own sanity.

Riddle's investigation reaches into the very identity of madness, but it takes one further, horrific turn when he is implicated in the serial killer's trail of murders.