in the dark, to be/keep someone

be in the dark

To not know something that other people do. Somehow, everyone knew that Alicia had quit school except for me—I was totally in the dark. No, I don't know who's going to get the promotion—now that I'm off the executive board, I'm in the dark about a lot of things.
See also: dark

keep someone in the dark

(about someone or something) Go to in the dark (about someone or something).
See also: dark, keep

keep someone in the dark

or

leave someone in the dark

If you keep someone in the dark or leave someone in the dark, you do not tell them about something In many cases, the government itself was being kept in the dark about what was going on. She thought you shouldn't be left in the dark but should be told as soon as possible.
See also: dark, keep, someone

keep someone in the dark

ensure that someone remains in a state of ignorance about something.
2003 Village Voice It's payback time for an administration that…has ignored lawmakers and…deliberately kept them in the dark.
See also: dark, keep, someone

in the dark, to be/keep someone

To be mystified or uninformed; to fail to inform someone. The figurative use of dark for ignorance is very old indeed. “We can’t keep it dark any longer,” wrote the Roman playwright Plautus (Aulularia, ca. 210 b.c.), and Shakespeare wrote, “Till then I’ll keep him dark” (All’s Well That Ends Well, 4.1).
See also: keep, someone