Julius's expression could be charitably characterized as "bleak," but if he has thoughts on Fitcher's candidacy for the newly discovered spy (and Marcus, at least, knows him well enough to suspect he does), he's holding his tongue. Bastien asked Marcus, specifically. Besides, Julius has nothing of use to contribute on the matter of "SF" or Marcus's particular enemies. For the time being, he occupies himself with the lock on Marcus's ankle and with keeping his expression at least somewhat level.