The Thirty-Nine Steps is a 1915 adventure novel by the Scottish author John Buchan, first published by William Blackwood and Sons, Edinburgh.

It was serialized in All-Story Weekly issues of 5 and 12 June 1915, and in Blackwood's Magazine (credited to "H. de V.") between July and September 1915, before being published in book form in October of that year.

Disillusioned with his uneventful life as a man about town, he is on the brink of resolving to leave England for good when a panicked neighbour, Franklin Scudder, knocks at the door of his flat in Portland Place.

Determined to warn the government of the plot, but unwilling to go to the police for fear of being arrested for murder, Hannay escapes the building disguised as a milkman and takes a train to Scotland, intending to find a remote area where he can lie low.

Hannay alights at a rural station in the Galloway Hills, and a cat-and-mouse chase ensues as he evades both the plotters, who attempt to spot him on the open hillside from an aeroplane, and the police.

Deciphering Scudder's notes, he learns that his adversaries are members of a German spy ring known as the "Black Stone" whose goal is to steal Britain's naval defence plans before war breaks out.

Hannay, now cleared of the Portland Place murder, is left to his own devices, but a general feeling of unease prompts him to call at Sir Walter's house.

Realising that the spies will have to cross the Channel to get their information back to Germany, Hannay and the meeting attendees comb Scudder's notebook for clues as to the planned point of departure.

Hannay confronts the occupants of the villa and is mortified to find what appears to be a perfectly ordinary group of English friends who have been enjoying a game of tennis in the sun.

[8] The Thirty-Nine Steps is one of the earliest examples of the '"man-on-the-run" thriller archetype subsequently adopted by film makers as a much-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.

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.

[2] It is closely based on Hitchcock's adaptation, including the music-hall finale with "Mr. Memory" and Hannay's escape from a train on the Forth Bridge, scenes not present in the book.

The 1978 version was directed by Don Sharp and starred Robert Powell as Hannay, Karen Dotrice as Alex, John Mills as Colonel Scudder.

[13] It is generally regarded as the closest to the book, being set at the same time as the novel, pre-Great War, but still bears little resemblance to Buchan's original story.

The film was followed by a spin-off television series, Hannay, also starring Powell and featuring adventures occurring before the events in The Thirty-Nine Steps.

The film ends with a scene involving a submarine in a Scottish loch, rather than the original setting off the Kent coast, and the apparent death of one character.