The Mindless Slaves of Dr. GroutSuperman Sunday Newspaper Strip - December 31, 1939 to February 4, 1940
Clark - and Superman - encounter their second mad scientist, the insidious Dr.Grout who hypnotizes unemployed men into becoming mindless assassins. 
As Superman makes short work of assorted thugs and ne’er-do-wells across multiple media, the cops-and-robbers elements of his stories increasingly give way to elements of science fiction. Ultra initiates the upcoming rogues gallery of mad scientists in the pages of Action, and in this arc of the color Sunday newspaper strips we’re introduced to Superman’s second evil scientific nemesis, “Dr.Grout” (A white-jacketed mesmerist who hypnotizes homeless men into becoming brainwashed assassins - some shades of “Reign of the Super Man” to be had).
Although Superman’s adventures up to this point are largely ground-level, you can at least say in his defense that he’s yet to repeat a theme - he’s put the boot to one wife-beater, one lynch mob, one war profiteer, one overzealous warden, one cruel orphanmaster, and so on. It’s one beating per offense in Superman’s world! 
But, of course, avoiding repetition among the violators of the social trust against whom Superman pits his tremendous strength means that the Man of Steel, in short order, will eventually find himself battling reckless drivers and pinball machine syndicates. Ultimately, labors which test his tremendous powers (and which, in turn, encourage the invention of new powers) become the order of the day, and a small army of mad scientists will lead Superman’s march into science fiction territory…

The Mindless Slaves of Dr. Grout
Superman Sunday Newspaper Strip - December 31, 1939 to February 4, 1940

Clark - and Superman - encounter their second mad scientist, the insidious Dr.Grout who hypnotizes unemployed men into becoming mindless assassins. 

As Superman makes short work of assorted thugs and ne’er-do-wells across multiple media, the cops-and-robbers elements of his stories increasingly give way to elements of science fiction. Ultra initiates the upcoming rogues gallery of mad scientists in the pages of Action, and in this arc of the color Sunday newspaper strips we’re introduced to Superman’s second evil scientific nemesis, “Dr.Grout” (A white-jacketed mesmerist who hypnotizes homeless men into becoming brainwashed assassins - some shades of “Reign of the Super Man” to be had).

Although Superman’s adventures up to this point are largely ground-level, you can at least say in his defense that he’s yet to repeat a theme - he’s put the boot to one wife-beater, one lynch mob, one war profiteer, one overzealous warden, one cruel orphanmaster, and so on. It’s one beating per offense in Superman’s world! 

But, of course, avoiding repetition among the violators of the social trust against whom Superman pits his tremendous strength means that the Man of Steel, in short order, will eventually find himself battling reckless drivers and pinball machine syndicates. Ultimately, labors which test his tremendous powers (and which, in turn, encourage the invention of new powers) become the order of the day, and a small army of mad scientists will lead Superman’s march into science fiction territory…