Graham is a British armaments engineer, due to travel back from Turkey, where he has completed technical preparations for a project to improve the Turkish navy.

His company's representative in Turkey, Kopeikin, takes him to an Istanbul nightclub, where he meets Josette, a Hungarian dancer.

A doctor dresses Graham's hand, and Kopeikin takes him to see Colonel Haki, the head of the secret police.

Graham identifies the man in the crumpled suit from a photograph, and Haki reveals this is Banat, a Romanian hired killer.

Also on board is an elderly German archaeologist Haller and his wife; a Turkish tobacco dealer Kuvetli; a French couple the Mathises; and an Italian lady with her son.

Yet ultimately the German professional pays dearly for underestimating this amateur — another plot element which was to be repeated in later Ambler books.

The book came to be regarded as a classic among spy thrillers, setting out what became some of the genre's basic conventions and immensely influencing later works including the James Bond series.

Part of the book's lasting charm is its capturing the atmosphere and mindset of the "Phony War" phase during which it was written: France is standing strong and nobody predicts the fall of France within a few months; the Italians are strictly neutral and there is no suggestion that they are about to ally with Germany against Britain; and so on.

Thus, though the plot of Ambler's book is fictional, it is set against a very concrete and real background - and at the time of writing, no one could have known for certain what Turkey's part in the war would be.

According to Norman Stone, Ambler's early novels are "halfway between Buchan and Bond, and the difference is the cinema."

Another film adaptation was made in 1975, Journey Into Fear, directed by Daniel Mann and starring Sam Waterston and Vincent Price.