Robert Wise on Henry Daniell: "Henry was as far from a complainer as any I've ever known. He'd walk onto the set, do his work like the pro he was, do it damn good, and then quietly leave without being a burden to anybody. Period."
Although based on a fictional short story by Robert Louis Stevenson, the author came up with the idea from actual events occurring in 19th century England and Scotland, particularly those of grave robbers Burke and Hare.
The quote from Robert Wise on Henry Daniell was a subtle dig at Boris Karloff who notoriously used his clout and SAG creator status and membership to complain about long hours and other miscellaneous details during production.
This bizarre final pairing between Bela Lugosi and Boris Karloff, with Karloff securing maximum screen time while having Lugosi relinquished to a "barely there" janitor role, is better understood when looking at the aftermath of their collaboration in Son of Frankenstein (1939): upset about the critical acclaim that Lugosi received for his portrayal as Ygor which eclipsed his slim appearance, Karloff refused to ever play the monster again, (particularly since Ygor would become a recurring character in the Frankenstein franchise!) or to ever appear in another film opposite Lugosi, unless he was the star with the most screen time. This also explains why Karloff appropriated the doctor role that was written specifically for Lugosi in their next major film, Black Friday (1940), thus leaving the Astro-Hungarian to play a minor, American gangster part his thick, albeit alluring, Hungarian accent made him ill-suited for, and forcing script changes to remove references to the doctor's past in Vienna, since Karloff himself spoke with a British accent. It is unclear whether Lugosi ever became aware of who was behind his recurring unfortunate "luck" in these films.