The Good Death Eater

It seems that there's a storyline that interests JKR enough that she's done it 3 times--the young man who joins the DEs and at some point finds himself possibly unable to continue. It's the man who gets in over his head. She did it with Snape, with Regulus, with Draco. What's frustrating is honestly it seems like whichever one you like best somehow is supposed to only do the second part--like he had a change of heart without doing wrong first. I was frustrated recently in a conversation about Regulus, though I also hear it about Snape and I know Draco too gets this kind of defense. ( They're Death Eaters. Get over it. )