Don't keep me in the dark, tell me what's really going on.
Tips
usage
This is a very common colloquial idiom. The structure is usually 被/把...蒙在鼓里. It's the direct equivalent of English 'kept in the dark' and is used in everyday conversation.
memory
Picture being sealed inside a big drum — you can't see anything, and all you hear is muffled noise. Everyone outside knows what's happening except you.