Wiktionary
skeleton in the cupboard
n. A shameful secret.
WordNet
skeleton in the cupboard
n. a scandal that is kept secret; "there must be a skeleton somewhere in that family's closet" [syn: skeleton, skeleton in the closet]
Usage examples of "skeleton in the cupboard".
But this sort of genius -- For a financial family a painter is rather a skeleton in the cupboard.
Why yes, there must be some skeleton in the cupboard or you wouldn't run him down.