This serial was written by Sax Rohmer, the author of the original Fu Manchu novels, and partially adapts the first book, The Mystery of Dr. Fu Manchu. Likely because the author was involved in it’s creation, it both looks and reads better than any of the earlier adaptations.
The character personified the racist idea of the “yellow peril” to such a degree that the name is still known, even though few have read the books. And in fact, one of the books is titled “The Yellow Peril.”
Dr. Fu Manchu is evil incarnate, basically, a chemist and poisoner out to bring down both “old” and “new” China and rule it himself. He controls the opium dens of London, but also has palatial countryside estates spread throughout England. He is pursued by Dennis Nayland-Smith and his sidekick, Dr. Petrie, as he murders men connected to his past in India, and kidnaps engineers.
The serial ends unfinished, so I was not clear on why Fu Manchu was doing this, but checking on wiki informed me that even in the books, his ultimate goals were never explained.
Dr. Fu Manchu: Detective Comics 17 -28 (July 38 = June 39)