This book follows the Mr. Moto formula for the most part, a brash callow young man and a strong-minded independent young woman, whom the young man thinks needs his protection, never mind that he's much more of an idiot than she is, find themselves inadvertently enmeshed in the middle of international intrigue in an Asian country, this time Mongolia. Mr. Moto, the Japanese secret agent, is pulling the strings in the background so that all will end up very, very nicely. The time is a few years before WWII, and the Japanese and Russians are vying to control northern China. The gateway between Russia and northern China is through Mongolia, and so both the Japanese and Russians are scheming to subvert a Mongolian prince into joining their side. Essentially, the issue is which of the two countries gets to have their armed forces "cooperate" with the prince in the defense of his own little bit of Mongolia.
This is a pretty good tale, and differs a bit from some of the previous Mr. Moto books in that Moto himself is a bit more prominent in the overall plot. In the first Mr. Moto book, he was barely present at all. As things have progressed through subsequent volumes, it seems that Mr. Moto becomes more central to the basic action and we get to know him a bit better each time. So there are two more Mr. Moto books, and there's zero chance I won't have read them by the time the New Year rolls around.