This was excellent! What a clever premise, and very well executed. I really like your young Snape voice. It's always fascinating to see someone's relationship with a parent, because there's an inherent vulnerability to that dynamic that is totally unique. You obviously get that and showed it beautifully here.
All the characters are well drawn but I'm just smitten with your Argus. He is who he is, not whitewashed, but the respect he shows for Irma is utterly charming. When he asked her to cast spells until she'd convinced herself it was okay, I found that very moving. You don't need to be educated to have sharp perceptions about what makes people tick.