Here's a look at what we have learned so far and what could be coming next in the Trump impeachment inquiry.

Charles Kupperman, who was a deputy to former national security adviser John Bolton, failed to show up for a scheduled closed-door deposition Monday. In a statement, he said he was awaiting "judicial clarity.''

Closed-door interviews are tentatively scheduled with Charles Kupperman, a deputy to national security adviser John Bolton, and Tim Morrison, the National Security Council's current Russia and Europe director.