keep in the dark
keep (someone) in the dark (about something)
To keep someone uninformed (about something); to exclude someone from full knowledge or disclosure (of something). Keeping taxpayers in the dark about how their money is being spent is not how government should operate. I don't fully trust John to keep our plan a secret, so I think it best that we keep him in the dark for now.
keep someone in the dark
(about someone or something) Go to in the dark (about someone or something).