My brother, she thought, still having a hard time wrapping her mind around that concept.
This chapter is mostly dialog, which exposes some of my earlier weaknesses in writing dialog. I hope I have improved. But the meat of it is Maximilian's explaining... most of the truth about their father to Alexandra, and why he is here at Charmbridge.
Max apologizes for the things he allowed to happen, including Alexandra getting Crucioed, but he's pretty blase about torturing and killing animals and watching as younger kids are seduced to the Dark side. Max may get a pass for his wobbly moral compass given that he's only sixteen, but he is already awfully good at rationalizing, just like his old man.
She wasn't sure that was true. She knew there was a part of her that would like very, very much to see John Manuelito writhing on the floor, screaming in pain. Then she remembered the look of terror on Tomo's face, and wondered if that part of herself was what the Boggart Tomo had seen looked like.
I have at various times in the series tried to hint at Alexandra's darker nature. A few readers have commented that they just don't buy it — sure, Alex has a temper, and she can be a brat, but when push comes to shove she always ends up doing the right thing and seems to have too many scruples (reluctant to kill, unwilling to torture, sees non-humans as people, won't even allow animals to be harmed) to be convincing as someone who could go Dark.
This is in line with some other comments to the effect that she's not ruthless enough, and hasn't yet gone out and demanded answers and taken what she needs.
So here I have to concede that I probably simply haven't succeeded in writing Alexandra's personality strongly enough in this respect. I am not commenting on whether Alex will ever "go Dark," but my original conception of her was someone that the readers would believe might, or at least could. Looking back, though, and even as I write book five, I realize that I've also written her as a product of her environment: a suburban, middle-class child who for all her "adventures" and her somewhat distant parents, has always been pretty safe and secure, at least until she entered the wizarding world.
She's naturally tough and learning to be tougher, but she didn't spend her childhood in the shadow of her father, and living on a remote island surrounded by creepy neighbors like her brother. Of course, Julia grew up just like Max, minus BMI. The difference between them is partly natural disposition (yes, Julia just really is that bubbly, and Max was born to be dour) and partly the fact that Abraham Thorn recruited Max.
(Are you asking: Why Max? Why none of his daughters? Is Abraham Thorn just a big old chauvinist? Heh.)
Note also that Alexandra is not the only one who has the charisma to gather a circle of talented friends:
“I hope so,” she muttered. Then she looked up at him again. “Hey, all this stuff you've been telling me – aren't you worried about the curse in that secrecy contract?”
“Oh, I already had it removed.” Maximilian smiled at her. “Martin's been studying curse-breaking for a couple of years now. He's not a professional, of course, but neither was whoever enchanted that contract.”
So Alex takes Honey back to Angelique, and leaves Darla and Angelique to sort out their, um, issues. Meanwhile, Anna is waiting up for her. Alexandra promises more explanations later (kind of like Max did to her, hmm?) and the next morning, she checks on Tomo. Then, after JROC drills, Maximilian pulls her aside, and he tells her the rest of the story. Well, most of it.
“Children? Other children?” Alexandra felt slightly dizzy at all the information spilling out of her half-brother.
Maximilian nodded. “You and I have four other sisters that I know of, besides Julia. I've met Lucilla and Drucilla, but not their younger sister Valeria – they're Father's daughters by his second wife. And I've heard he had a daughter by his first wife.” He added bitterly: “All of us get interviewed by the Office of Special Inquisitions, at least a couple of times a year.”
Max had heard of Livia, thought not by name, but of course he didn't know about Claudia.
“And you're supposed to infiltrate them?” she asked incredulously. “And the WJD let you, because you're Abraham Thorn's son and they figured the Dark Convention would be extra-interested in you? And then what? You rat out the Mors Mortis Society, help them arrest some Dark wizards? What's in it for you? All they want is to catch our father, and they don't mind using us to do it! And you're willing to cooperate with them? Will you turn him in, too, if you get a chance?”
Max's version of the story is that he's been planted at Charmbridge to infiltrate the Mors Mortis Society for the Wizard Justice Department. Of course, as we learn later, he's a double agent.
After all this revelation, Max praises her fierceness and her talent, and Alexandra, in spite of herself, and though she doesn't realize it yet, is starting to melt.
Annoyed, she snorted and shook her head, but as much as she wanted to tell him off, there was something about his earnest expression that stirred feelings in her for which she had no name. Maximilian was an arrogant, hot-tempered jerk and a condescending bully. But now she was seeing another side of him: tough, brave, skilled, determined, ambitious. And protective. She had never had a brother, and she still didn't know how she felt about having one suddenly appear in her life.
This was basically an infodump chapter. The writing could have been stronger, but this was the big reveal about Maximilian and Abraham Thorn and all the children of Thorn, and set the stage for everything that followed: Maximilian's relationship with Alexandra, and of course, his mission.

It's not easy to mock up uniforms if you have minimal graphic arts skills like me. But I was disproportionately pleased with these, even if I did have to Photoshop the hell out of all the defects. Alex's expression is great, too. I like the perspective, but Max clearly looks way too tall, since Alexandra is not that short.