skeleton in closet
skeleton in the/(one's) closet
An embarrassing or shameful secret. Primarily heard in US. If you've got a skeleton in the closet, it will probably be exposed during this campaign. He didn't believe me when I said that I didn't have any skeletons in my closet.
skeleton in (one's) closet
A source of shame or disgrace, as in a family, that is kept secret.