他们逮捕的那位因进行间谍活动的高级文职人员，原来是20年前敌人情报机构安插的特洛伊木马。 The senior civil servant they arrested for spying turned out to be a Trojan horse, planted by enemy intelligence twenty years previously.
这一事件理所当然地堪称是国王间谍活动的的独一无二的史诗。 The episode could reasonably serve as a unique epic of royal espionage!
间谍的，惊险的以戏剧性的阴谋为特征的，常常指间谍活动 Marked by melodramatic intrigue and often espionage.
他正在干间谍活动时被抓住了。 He was caught in the very act of espionage.