This is such a rich mystery, one that loops back on itself. Although one reading satisfies all the criteria for a great mystery, a second reading reveals how sly the author is in conveying what is a very dark vision of human motivations. I won't give any more away. Suffice to say, the atmosphere, the plotting, the insight into the psychological motivations and motives of the characters, and the knowing presentation of the British operations in the Territories gives this an all-too credible feel. On first reading, the horrible secret may seem dated, but on the second reading, with all the plot and character machinations truly revealed, the secret becomes all too appaling. This book was very hard to find in the stores, by the way. Enjoy!