From Publishers Weekly Denham's second whodunit fully measures up to his applauded debut in The Man Who Lost His Shadow. The "Two Thyrdes" are father and son; the story alternates between descriptions of the former's dicey adventures in 1945 and the latter's troubles， 35 years later. During WW II， Viscount Derek Thyrde is killed before he can determine which of his peers in the House of Lords is a spy for the Nazis. Married and an expectant father， Derek leaves a document， with clues to the traitor， in trust for his son， also named Derek. The young viscount faces the dangerous task of identifying the man guilty of treason， when the spy frames the second Thyrde with planted evidence of theft. The swift， exciting story is colored by effects marking the differences between "then" and "now，" particularly in the social climate and the conduct of lovers. February 4Copyright 1985 Reed Business Information， Inc.