The Levanter — Eric Ambler

Winner of the Crime Writers' Association Gold Dagger Award
 
Syria, 1970. Michael Howell has kept his family's Middle Eastern business enterprises going through a decade of takeovers, war, and revolution, thanks in part to his office manager, Teresa, who is also his mistress. One late night at the office, they discover men working overtime -- producing unauthorized bombs for the Palestine Action Force. Worse, this guerrilla terrorist group is not deterred by their discovery -- rather, they will enlist Howell and Teresa's unwilling help in carrying out their plan.