know where the bodies are buried
know where (all) the bodies are buried
To know a large amount of secret or scandalous information about a person or group that they would not want to be revealed, especially due to one's lengthy experience with that person or group. Often used in relation to one who wields this information for their own benefit or advantage. I've been an accountant with this company for over 50 years, so trust me, I know where all the bodies are buried. He climbed to power because he worked for several top government and military officials and he knew where the bodies were buried.