American writer Howard Ingham arrives in the sweltering heat of Tunisia in search of inspiration for a new movie script he has been commissioned to write.

He gets to know Francis J. Adams, an aging American propagandist, and Anders Jensen, a Danish homosexual painter.

While waiting for a letter from his New York girlfriend, he settled on a plot for his projected novel, the story of a banker who forges documents to steal money he then gives to the poor.

Ingham struggles to keep this incident secret from his acquaintances while at the same time questioning Western morality, in particular the application of its principles in a country where he lives as a stranger.

- Julian Symons "Miss Highsmith's finest novel to my mind is The Tremor of Forgery, and if I were to be asked what it is about I would reply, 'Apprehension'."