The Thirty-Nine Steps first appeared in Blackwoods Magazine in August and September 1915 and depicts Europe on the edge of war in May and June 1914. It quickly became popular reading in the trenches and on the home front, and nearly a hundred years and three film adaptations later, its popularity is enduring. In a special edition of Free Thinking, as part of Radio 3's focus on World War One, Matthew Sweet talks to Buchan's biographer Andrew Lownie and Buchan scholars Dr Michael Redley and Dr Kate Macdonald about the connections between Buchan's own war experience and The 39 Steps, and to Professors Elleke Boehmer and Terence Ranger about how ideas about empire and adventure play out in the novel.