Sentence:  A similar tone of underlying futility and despair pervades the <WSD>spy</WSD> thrillers of Eric Ambler and dominates the most famous of all American mystery stories , Dashiell Hammett 's The Maltese Falcon . 
Meaning of the word marked with <WSD> tags:  (military) a secret agent hired by a state to obtain information about its enemies or by a business to obtain industrial secrets from competitors