The Thirty-Nine Steps

"The Thirty-Nine Steps" was written by John Buchan and published in the year 1915. It is only the first of the 5-book series of the Richard Hannay novels. 
This exciting action-adventure story was the inspiration for Alfred Hitchcock’s 1939 classic film of the same name.

Told from the first-person point of view, it relates the adventure of "ordinary fellow" Richard Hannay, who is thrust into a plot involving the theft of crucial military intelligence by German anarchists.
The novel begins as Richard Hannay has just arrived back in London after an extensive stay in South Africa. Hannay is accustomed to a fast-paced lifestyle and quickly tires of the London scene. Shortly after his return home, he meets a secret agent who believes that Great Britain is on the verge of a war with Germany and warns Hannay to be on the lookout for a group of assassins, collectively known as The Black Stone. The man hides in Hannay's apartment for a while.
Soon after this encounter, the spy is found murdered in Hannay's apartment; the spy has also left a notebook behind. Knowing that he may be implicated in the death of the spy and fearing for his life, Hannay flees London and follows his assassins to Scotland. On the way there, he decodes the spy's notebook and finds out how the Germans plan to launch the attack...