John Buchan 
The Island of Sheep 

The Island of Sheep (1936) is a novel by John Buchan. It is the last of his novels to revolve around Richard Hannay and Sandy Arbuthnot.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.