"It was dusk, on the evening of December 7, 1906, when I first encountered Sir John Harmon. At the moment of his entrance, I was standing over the table in my study, a lighted match in my cupped hands and a pipe between my teeth. The pipe was never lit." So begins this short story by Hugh B Cave where an uncanny device takes possession of the minds of "law abiding citizens" and molds them into murdering tools. A rather mad scientist combines hypnotic waves with radio waves, and thus The Murder Machine.