“蒙在鼓里”，字面意思是被包在鼓里（literally be kept in a drum）；比喻受人蒙蔽，对有关的事情一点儿也不知道。可以翻译为“be kept in the dark”。

例句：

全村都知道了，他还蒙在鼓里。

The whole village knew about it, but he was still kept in the dark.

谢谢你给我透了个信，我真是蒙在鼓里呀!

Thank you for bringing me the news. I've been living in the dark till now!