In Plain Sight (US): Season 3, Episode 4

3 - 4: Whistle Stop

Mary and Marshall try to help FBI Agent Mike Faber (Steven Weber) convince his informant (Geoffrey Blake) to enter WITSEC. Despite their best efforts, the informant refuses their protection and gets himself into a heap of trouble. Meanwhile, Stan has to deal with an ex-boxer/witness (Chad Coleman) suffering from pugilistic dementia.