The Enemy Within — John Creasey

Department Z faces its biggest test when the organization is threatened by an enemy on the inside -- from the author who sold eighty million books worldwide.

Charles Corliss, son of a murdered agent from Department Z, seems like the perfect recruit for the ultra-secret spy organization. But when things start going seriously wrong, the agents begin to suspect this charming young man is not as loyal as he first seemed. Filled with hate for the organization that allowed the death of his father, Charles begins to sabotage the department as a double agent dedicated to the Communist cause.

“Mr. Creasey realizes that it is the principal business of thrillers to thrill.” -- Church Times

“Little appears in the newspapers about the Secret Service, but that little makes anything on the subject probable fiction. Mr. Creasey proves himself worthy of the chance.” -- The Times Literary Supplement