To keep dark

to reveal nothing.

See also: Dark

References in classic literature ?
You know something about that Spaniard that you want to keep dark.
Villagers struggle to keep dark secrets at bay as she pursues the truth.
Since taking office, Governor Bullock has fought to keep dark money out of politics and championed measures to increase transparency in Montanas elections.
He is, the narrative goes, a sad wreck of a man, chainsmoking and drinking himself into an early grave with his endless Martinis with only a success of meaningless onenight stands to keep dark thoughts at bay.
Experts say that in the earlier days the so-called cursed people often filled bottles with bent toenails and fingernails, urine, and hair to keep dark spirits away.
When Prosecuting lawyer Geoffrey Millar QC put it to the defendant he "wanted to keep dark and secret that which was going in in the pastoral centre between you", Fr Crilly replied: "That is not true.
Put a MAC Studio Touch Up Stick (a medium coverage concealer) into your handbag to keep dark circles, spots or blemishes hidden.