Journey into Fear by Eric Ambler

Returning to his hotel room after a late-night flirtation with a cabaret dancer at an Istanbul boîte, Graham is surprised by an intruder with a gun. What follows is a nightmare of intrigue for the English armaments engineer as he makes his way home aboard an Italian freighter. Among the passengers are a couple of Nazi assassins intent on preventing his returning to England with plans for a Turkish defense system, the seductive cabaret dancer and her manager husband, and a number of surprising allies. Thrilling, intense, and masterfully plotted, Journey Into Fear is a classic suspense tale from one of the founders of the genre