whistle in the dark

blow the whistle

To disclose information to the public or to appropriate authorities concerning the illegal or socially harmful actions of a person or group, especially a corporation or government agency.

clean as a whistle

Very clean.

dark cloud

A situation or future event that causes worry, problems or unhappiness, likened to such a cloud overhead in the sky.

dark horse

Someone who possesses talents or favorable characteristics that are not known or expected by others.

look on the dark side

To examine a situation, usually unfavorable, from a negative perspective; to be pessimistic or miserable.

not worth a whistle

Worthless or pointless.

oh dark hundred

Some unspecified hour in the early morning (implies an unpleasant time to be awake)

oh dark thirty

Some unspecified hour in the early morning (implying an unpleasant time to be awake).