This story has been reported for weeks by Levin, Hannity, Carlson, Dick Morris--(yep you might not like him, but he is smart and is staying up on this stuff. He has a channel on Youtube). Probably others, too.
A case can be made for Flynn to withdraw his guilty plea. A case can be made to halt Mueller entirely.
Supposedly Sessions had the DOJ-IG study the whole deal.
How many other layers on these onions, and how it blows up later makes for good political drama and intrigue.