[Julian Symons] has been putting together intricately crafted and plotted novels for roughly four decades, earning along the way more respect from peers than public fame…. [Symons] is not so well known as [Eric Ambler, Graham Greene, and Daphne du Maurier], but like them he can invest a plot with significance beyond its conclusion…. Yet he may now be on the brink of solving the mystery of his comparative obscurity. At an age when most writers are, to put it gently, no longer productive, he is overseeing the publication of two new books on the same day. Taken together, they may prove a case to a wider array of jurors: Symons is far more than a maker of puzzles; he is a master of moral conundrums.

Exhibit No. 1 is The Detling Secret, a novel molded into the shape of the classic whodunit. The setting is England, the time...