If Muellhead were an honorable man he would drop the charge. He knew the FBI agent he used in his investigation was a lapdog for HRC and anti-Trumper and yet he used him to question Flynn which set up the charge. Then he hid this information from the oversight committee and would not allow him to testify until he got his plea agreement in.
The plea included the immunity deal and release from prior NDA during his Obama years for Flynn to tell all - Trump can always pardon him down the road.