(I'm reading The Insidious Dr. Fu-Manchu, also known as The Mystery of Dr. Fu-Manchu. Originally published as short stories, this chapter begins the third which my half-hearted research suggests may be called Redmoat.)
Smith elaborates on Rev Eltham's past; he is in fact Parson Dan, the Fighting Missionary, famous or notorious for defending the hospital at Nan-Yang during the Boxer Rebellion*.
As the evening goes on the reverend gives us quite a bit of exposition. After a burglar tried to rob him of his "collection" he re-fortified the priory; although the moat is dry it is still a good twenty feet from bottom to top of the wall, and now covered in barbed wire. The only entrance is through a cutting with a gate at either end; in addition the barbed wire and gates have been given the most modern of anti-burglary defences; electric bells that ring when they are interfered with. Previously there were two dogs, but unfortunately the collie that belonged to Denby, Rev Eltham's nephew, has been bludgeoned to death. Nasty. Fu-Manchu clearly has a lot to answer for.
Smith is still puzzled by the timing of events, until the reverend reveals that he intends to return to Nan-Yang. "Smith jumped round upon him as though moved by a spring." Eltham has been warned by the Mandarin Yen-Sun-Yat not to go. Smith has a few things to say: "The Mandarin Yen-Sun-Yat is one of the seven!" and "China to-day is not the China of '98. It is a huge secret machine, and Ho-Nan** one of its most important wheels!"
He urges Eltham not to go to China, but the reverend insists that only one can prevent him. Smith replies "Then only One can protect you, for, by Heaven, no MAN will be able to do so!" The one they are talking about is god if that's not clear for some reason.
Smith tries his ultimate argument: "The phantom Yellow Peril," said Nayland Smith, "to-day materializes
under the very eyes of the Western world." and "We take the proffered right hand of friendship nor inquire if the hidden left holds a knife!" Eltham scoffs at first but promises to consider and talk again tomorrow. At that moment there is a scream.
"My God, it's Greba!" whispered Mr. Eltham. Quick! Rush to save her (in Chapter 8)
* The Boxer Rebellion is pretty complex, but you know, what isn't. I recommend A Brief History of the Boxer Rebellion by Diana Preston if you wish to know more.
** I believe that the Wade-Giles romanisation Ho-Nan is Henan province in pinyin. Thanks in part to new railways at the time Rohmer was writing Henan was modernising under the new Republic of China, so Smith's assertion is not entirely unjustified.