暗探

例句：

1. 1. He is an expert in the field of dark investigations.
   他是暗探领域的专家。
2. 2.The undercover agent successfully infiltrated the enemy base.
   这位卧底特工成功地渗透了敌人的基地。
3. 3.The spy revealed that the government had been leaking secrets to the opposition.
   间谍透露政府向反对派泄露了机密。