Possibly the very first instance where Hollywood produced a 'prequel,' because this last entry in the series depicts the first meeting between Mr. Wong and Capt. Street.
The last of the six-film series, and the only one not to star Boris Karloff, replaced by Keye Luke. Monogram owed the distributors one more Wong feature, and had completed Karloff's six-picture contract with the horror film The Ape.
This was the only Hollywood film of the period in which an Asian detective was played by, and top billing was given to, an actor (Keye Luke) who was actually Asian.