know where (all) the skeletons 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. Such information is usually gained through one's lengthy experience with that person or group. A variant of the more common phrase "know where (all) the bodies are buried." I've been an accountant with this company for over 50 years, so trust me, I know where all the skeletons are buried. He climbed to power because he worked for several top government and military officials and knew where the skeletons were buried.