Words (and phrases) to know: ‘in the dark’

This idiom means to be kept without information.

•  Adam has know all along just how serious their money situation is, but he’s kept Lauren in the dark because he didn’t want her to worry.
• Voters complain that the government wants to keep them in the dark about that is really going on.

Notice that the pronoun is always inside the phrase: “to keep them in the dark” (not “to keep in the dark them“).