The investigator unsheathed the financial fraud that had been hidden by the company for years.

unsheathed 是动词 unsheathe 的过去式，由前缀 un-（表示"去除"）和动词 sheathe（"插入鞘中"）组成，字面意思是"从鞘中拔出"。在这里比喻为"揭露、使暴露"，就像把剑从剑鞘中拔出一样，把隐藏的真相暴露出来。