蒙在鼓里 kept in the dark
Explanation
比喻受蒙蔽，对事情一无所知。
A metaphor for being kept in the dark, knowing nothing about something.
Origin Story
从前，在一个偏僻的小山村里，住着一位名叫阿牛的年轻人。阿牛为人老实憨厚，却总容易被别人蒙蔽。一天，村里来了个江湖郎中，自称能治百病，还表演了许多神奇的医术，村民们纷纷掏钱求医。阿牛起初有些怀疑，但郎中信誓旦旦地保证，阿牛最终还是相信了，并掏光了家底请郎中为自己久病的母亲治病。郎中收了钱，却只给了阿牛几包普通的草药，根本没有认真医治。阿牛的母亲病情并没有好转，反而更加严重。阿牛一直蒙在鼓里，直到村里有人揭露郎中是骗子，阿牛才恍然大悟，痛悔不已。从此以后，阿牛变得更加谨慎，不再轻易相信别人的花言巧语，也学会了独立思考，不再轻易被蒙在鼓里。
Once upon a time, in a remote mountain village, lived a young man named An Niu. An Niu was honest and kind-hearted, but he was always easily deceived. One day, a traveling doctor came to the village, claiming to be able to cure all diseases. He performed many amazing medical feats, and the villagers paid him a lot of money for his services. An Niu was initially skeptical, but the doctor assured him that he could help his sick mother. An Niu gave the doctor all his money, but the doctor only gave him a few packets of ordinary herbs, without seriously treating his mother. His mother's condition did not improve, but rather worsened. An Niu remained in the dark until a villager exposed the doctor as a fraud. An Niu realized his mistake and learned to be more cautious and not believe so easily.
Usage
多用于口语，形容对某事完全不知情。
Mostly used in spoken Chinese to describe being completely unaware of something.
Examples
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他一直被蒙在鼓里，直到事情败露才真相大白。
ta yizhi bei meng zai gu li, zhidao shiqing bailu cai zhenxiang dabai.
He was kept in the dark until the matter was exposed.
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会议的最终决定，他竟然蒙在鼓里，一点也不知道。
huiyi de zui zhong jueding, ta jingran meng zai gu li, yidian ye bu zhidao.
He was completely in the dark about the final decision of the meeting.