well the man with the ring is the mysterious man that has kidnapped(?) Neal's gf Kate (Neal has a pic of the right hand of the guy on her shoulder) and in the last episode Neal gets evidence that that guy is close to him and he thinks he's some FBI guy he just met and in the last scene there's Peter wearing the ring and greeting Kate in a hotel room saying "hello Kate" so it was like "omgwtf he's the man with the ring? but what about the bromance?"