John Buchan 
The Island of Sheep [EPUB ebook] 

First published in 1936, ‘The Island of Sheep’ (or ‘The Man from the Norlands’ as it is known in the United States) is the fifth and final of the series of Richard Hannay ‘spy’ novels by John Buchan.
The action occurs twelve years later on from the last novel, when Hannay, now in his fifties, is called by an old oath to protect the son of a man he once knew, who is also heir to the secret of a great treasure. He obtains help from Sandy Arbuthnot, now Lord Clanroyden, and Lombard. The action takes place in England, Scotland and on the Island of Sheep.