The book has no dedication, but opens with a quotation from Shelley's 1818 poem, The Revolt of Islam (Canto 1, Stanza 29).
Fear, Hatred, Faith and Tyranny, who spread
Those subtle nets which snare the living and the dead.
This is Canning's only thriller set entirely behind the Iron Curtain. It takes place around Dubrovnik in what was then Yugoslavia, and features a British engineer, Robert Hudson, unwillingly involved in espionage and suspected by the police chief, Zarko. It is one of Canning's best works from this period, owing a little perhaps to his friend Eric Ambler.
This was Canning's fourth post-war book for Hodder and Stoughton, published in 1950 at 8/6 with a print run of 12,000 copies. The US edition by Mill & Co came out in the same year. Hodder and Stoughton issued a reprint in 1952 at 6/-, later raising the price to 10/6. In 1957 a comic strip version was issued in Super Detective Library No 84. Happily there is a new editon, both e-book and p-o-d, from Bello, the "modern classics" imprint of Pan Macmillan.
Surprisingly, it was never filmed.
A very positive and detailed review has recently appeared in Mike Ripley's excellent Getting Away With Murder blog.