take (someone) into (one's) confidence
To tell someone information with the understanding that they will not reveal what was said. Daniel, we've taken you into our confidence to discuss the direction of the company, and where we see you fitting into it. You're the only person I've taken into my confidence about this, so please don't discuss it with anyone else.
take someone into one's confidence
to trust someone with confidential information; to tell a secret to someone and trust the person to keep the secret. We are good friends, but I didn't feel I could take her into my confidence. I know something very important about Jean. Can I take you into my confidence?