Richard Hannay

A thriller novel series by John Buchan, featuring the eponymous spy.

The novels, in order:
 * 1) The Thirty-Nine Steps (1915)
 * 2) Greenmantle (1916): Hannay and four friends make their way through wartime Europe to Turkey, searching for the truth behind the rumours of a German secret weapon that could throw the entire Muslim world into the war on the Germans' side. Sometimes considered to be one of the best books Buchan ever wrote; Hitchcock wanted to film it for years but never got around to it.
 * 3) Mr Standfast [sic] (1919): An old enemy reappears and in the last pivotal days of World War I on the Western Front, Hannay wages a battle of wits. Finally introduces a Love Interest (she's worth the wait).
 * 4) The Three Hostages (1924): With World War I over, Sir Richard and Lady Hannay are enjoying a quiet life in the country, but when three young people are kidnapped and a mind-controlling genius starts leaving cryptic clues behind, the pair of former spy-hunters have to go back to work.
 * 5) The Island of Sheep (1936): Set roughly fourteen years after The Three Hostages. Hannay and his son Peter John Hannay have to protect an old friend from fortune-hunters.

See the individual work pages for the applicable tropes.