John Buchan’s The Thirty-Nine Steps is a superb boys’-own adventure: wonderfully tense, gloriously improbable, and carrying enough imperial confidence to make a modern reader wince impressively.

One of my favourite moments is incredibly unsettling.

Hannay finds himself looking across a table at a group of men, trying to work out whether they are the enemy. They seem perfectly ordinary. There is nothing he can point to with certainty. He is forced to make a judgement without knowing whether he can trust what he sees — or his own interpretation of it.

They seemed exactly what they professed to be, and I could not have sworn to one of them.

That uncertainty is one of the things I find so interesting about the thriller. The detective story promises that careful observation will eventually make the world intelligible. But what happens when observation isn’t enough?

---

It’s a question Philip K. Dick takes somewhere considerably stranger. The question of knowing what is ‘real’ was a huge concern of his, and what – in the end – is more appalling than not knowing?

In Do Androids Dream of Electric Sheep? (1968) – the inspiration for the Blade Runner films – Deckard’s world becomes increasingly difficult to trust: even the existence of a parallel police force, complete with another Blade Runner, Phil Resch, makes him question what is real and what he can know about the people (and the world) around him. Much as I love the films, I can’t recommend the book enough, by the way: it’s so different, it really repays the read.

---

Buchan gives us the moment of doubt.

PKD turns that doubt into a worldview.

Maybe that’s one reason The Thirty-Nine Steps still feels more interesting to me than its reputation as simply a ripping yarn might suggest.

Over to you: tell me about a text you’ve read where a character’s version of reality is in doubt.