Someone wanted Department Z, the counter-espionage unit of the country, smashed once and for all; and this someone headed an organization so well co-ordinated as to anticipate the Department's every move. Was there an enemy within the gates? Or was Ryall, the Deparment man they had captured, being forced to reveal his knowledge whilst held as "a kind of prisoner"? Or was Ryall dead? And was the Department doomed to extinction?