Patrick Fitzgerald's original charge was to discover whether a crime had been committed in the disclosure by two Senior Administration Officials that Joe Wilson's tea drinking odyssey in Niger had been initiated by a suggestion from the well known (in some circles) CIA analyst Valerie Plame, who had the great good fortune to know Ambassador Wilson on a rather personal basis.
Mr. Fitzgerald, having lost his way very early in the investigation, has submitted an affidavit making the rather entertaining claim that one of Novak's sources (unnamed government official - UGO) might suffer in some way were his name to be disclosed. Mr. Fitzgerald very carefully redacted that name from the affidavit which has given rise to a great deal of speculation over at the Just One Minute blog (Plame Central for aficionados).
A very industrious commenter by the 'name' of MJW at JOM has spent a good deal of time and effort on his own investigation into the identity of UGO based upon a very careful analysis of the affidavit using some techniques reminiscent of those used in discovering the TANG memo fraud. The analysis is somewhat lengthy and can be followed here: