In The Three Hostages Buchan was uncannily prescient, telegraphing the coming financial collapse and the mass appeal of the fascists demagogues, particularly the resentment and malaise in Germany that spawned Hitler’s rise to power.

The allusion to the novel and the plot quoted give me the impression of the picaresque series of events as being nearly providentially arranged to keep the British cause and secrets hidden for a successful issue of their mission during WWI.The picaresque adds the element of unpredictability to a purposeful ending.Hitchcock’s renedering of the man on the run and his adaptation add fanciful elements aplenty to what is a fanciful yet purposeful account. JUST MY THOUGHTS.
QUOTE NOTED BELOW FROM CITED ARTICLES
“In May 1914, Europe is close to war and spies are everywhere. Richard Hannay has just returned to London from Rhodesia in order to begin a new life, when a freelance spy called Franklin P. Scudder calls on him to ask for help. Scudder reveals to Hannay that he has uncovered a German plot to murder the Greek Premier and steal British plans for the outbreak of war. Scudder claims to be following a ring of German spies called the Black Stone.

A few days later, Hannay returns to his flat to find Scudder murdered. If Hannay goes to the police, he will be arrested for Scudder’s murder. Hannay decides to continue Scudder’s work and his adventure begins. He escapes from the German spies watching the house and makes his way to Scotland, pursued both by the spies and by the police.

The mysterious phrase Thirty-nine Steps first mentioned by Scudder becomes the title of the novel and the solution to its meaning is a thread that runs through the whole story”
Literary significance and criticism
The Thirty-Nine Steps is one of the earliest examples of the ‘man-on-the-run’ thriller archetype subsequently adopted by Hollywood as an often-used plot device. In The Thirty-Nine Steps, Buchan holds up Richard Hannay as an example to his readers of an ordinary man who puts his country’s interests before his own safety. The story was a great success with the men in the First World War trenches. One soldier wrote to Buchan, “The story is greatly appreciated in the midst of mud and rain and shells, and all that could make trench life depressing.”

Richard Hannay continued his adventures in four subsequent books. Two were set during the war when Hannay continued his undercover work against the Germans and their allies the Turks in Greenmantle and Mr Standfast. The other two stories, The Three Hostages and The Island of Sheep were set in the post war period when Hannay’s opponents were criminal gangs.