Hannibal premiered to only about 4.3 million viewers and a 1.6 rating among adults 18-49 last week. But that was better than its special Go On lead-in and better than what NBC has been delivering in that slot for a year. Starting at that level, against tough competition on Thursday night, the odds are stacked against Hannibal building in the coming weeks, but it has happened before — Chicago Fire proved NBC can grow a number at 10 p.m. earlier this season.