SOUTHEAST ASIA during World War II is also the setting for this novel. (Apparently thriller readers and writers are becoming satiated with the Nazis; the only surprising thing is that it has taken them so long to catch on to the usefulness of the Japanese as sneering villains.) The title refers to the hour of twilight in the ancient Chinese clock, and the book begins with the fall of Hong Kong to the Japanese at Christmas of 1941. But, as Mather demonstrates, the descent of darkness is not, to the Chinese, a time of dying, but rather one of peace and rest before the next day's work begins. So it proves for Vincent Stafford, a wealthy Hong Kong businessman who evades the occupying Japanese troops and makes his way, through innumerable perils, to Chiang Kai-shek's headquarters at Chunking, a thousand miles away. Though there are excellent descriptions of political and military activity in this remote and little-known theater of war, Hour of the Dog is not a war book; it is an espionage-escape thriller, in the best Buchan-esque tradition. Stafford's wry humor and self-deprecation are reminiscent of Richard Hannay, and, like Hannay, he encounters a series of bizarre personalities as he travels the "ratline" --the underground railway through enemey lines to the dubious safety of the Nationalist Chinese hinterland. He must contend, not only with the Japanese, but with the warring factions of Chiang and Mao, traitors and double-agents. Dick Hannay was a trifle awkward with women; Stafford does better with his lady-love, a beautiful, courageous White Russian named Shivka. The minor characters are marvelous--Raucous, the British tommy and his Chinese girlfriend Aggie, who accompany Stafford on his hair-raising escape from Hong Kong; the two prim little English ladies, who staff one of the way stations on the escape route; Stafford's tough old mother Abigail, matriarch of the family; and countless others. Mather has written two other books about the Stafford family; this one is good enough to send readers who are not familiar with the earlier volumes of the sage trotting back to the library or the bookstore.