This was the last Charlie Chan movie produced by "20th Century Fox Studios," for America's entry into World War II in December 1941, shortly after this movie was filmed, made the studio cut back on film productions for the war effort.
The castle interior recycled the still-standing set from the first entry in the Basil Rathbone Sherlock Holmes series, The Hound of the Baskervilles (1939).
Naming the residents of the isolated castle Manderley is an obvious reference the the mansion of "Rebecca (1940)" from two years earlier.
The thirtieth of forty-seven Charlie Chan movies.