Except, Harry already knew. And as soon as they were home, he was going to know it all, every bit.
---------------------------------------------------
"All right, what gives?" asked Harry, the instant the three of them were back behind the safety of the adoption wards. "What is Remus hiding?"
Snape raised an eyebrow, his expression so blank that if Harry didn't know better, he'd think the man had no information at all. "I beg your pardon?"
Harry wasn't about to fall for that. "I saw you Legilimising Remus, and I know he did something he didn't report on, or at least, not to the full Order. What was it?"
"I'm really not at liberty to discuss the matter," said Snape, crossing the room, his gait so stiff that his robes didn't flutter like usual.
When Snape sat down, Harry dragged a chair close and did the same. "Look, I know you told Remus you wouldn't tell me, but--"
"Oh, you know that, do you?"
Draco rolled his eyes. "Harry, half the art of eavesdropping is not mentioning afterwards that you did it."
"I don't care," Harry shot back, rounding on Snape again. "You can punish me however you like, but first, we're going to settle this."
"One day past your birthday and you think you're in charge, here?"
Harry wasn't about to get sidetracked. "What I think," he said, stressing the phrase like Snape always did, "is that I've done what you kept asking me to do, namely, wait until we're home to have an argument. And I can say any stupid thing I like to you here, can't I? Isn't that what you promised?"
Snape's nostrils flared. "Manipulating me, Harry?"
"We're getting a long way from the point. You don't want to tell me what Remus is hiding, I know, but--"
"And I wouldn't have." Snape bared his teeth. "The matter is Lupin's to share or not, as he chooses, the details not mine to dispense. But now, Harry, I am not at liberty to discuss the matter at all."
Something about Snape's phrasing, or maybe his tone of voice, made Harry go still. The hairs on the back of his neck rose up, and stood on end as a chill swept straight through him. "Oh. Oh, no. You don't mean you won't, you mean you can't, I think. Er . . . Fidelius?"
"A variant thereof. I am conjoined not to divulge privileged information save to those who already know."
Harry's forehead wrinkled. "How is that different from the usual Fidelius charm?"
Snape snorted. "I alone am bound. Lupin is free to say anything to anyone, at any time."
Oh. Harry could see why that would irritate the hell out of his father.
"Well, he has to be," said Draco, speaking calmly, like he thought Snape was about to completely lose his temper. "If the Dark Lord punished Lupin for this whatever, then he already knows. Lupin can't be put in a position where it's clear he's under Fidelius. What if the Dark Lord orders him to tell the other Death Eaters what he did?"
"Albus' reasoning exactly." Snape crossed his arms and leaned back.
"Why not just make Lupin the Secret Keeper?"
"And you raised among the Dark Arts. Can you really not reason that out?"
"Oh . . . the Dark Lord might sense a change in his magic?"
Snape gave a sharp nod.
Harry felt fed-up by then, on several levels. "Why rail at Remus for saying the Dark Lord, if you're going to keep saying it yourself?"
Draco flushed, just a little. "Well, it sounds all wrong coming from him."
"If Lupin is idiotic enough to get used to saying Voldemort at this critical juncture-- but he's not. In fact, he's doing quite well, all things told." Snape's lips twisted, the expression bitter. "I wouldn't have believed it."
"How can he be doing well at his assignment, if he's ending up on the wrong end of Voldemort's wand?" cried Harry. "He was Crucio'd something awful! I could tell!"
"As could I. But Harry? I'm quite sure you understand now, that I cannot answer your question."
"Fidelius, right." Harry scowled. "But you weren't going to tell me, anyway!"
"True."
Snape's calm tone was too much for Harry to take. "How can you sit there and admit it? We're family! We're not supposed to be keeping secrets from one another!"
Snape's dark eyes flashed something dangerous-looking. "Draco. Your petite amie, was she untouched by man when you first met her? And if so, does she remain so?"
Draco's mouth dropped open. "You can't ask me that!"
"But I thought we weren't supposed to keep secrets," retorted Snape, in tones of mock-innocence. "Doesn't that give me leave to pry into your private business?"
"That's Rhiannon's private business!"
"As this is Lupin's," said Snape, facing Harry again. "And he specifically asked me not to tell you."
"It's not the same--"
"It's not sexual. Other than that, it is the same. Particularly since I was never in Lupin's confidence in the first place. What knowledge I have was acquired through stealth. All the more reason to respect his confidence, in my view."
"Confidence, ha," said Harry. "You think he has any in you, when he got you put under Fidelius so you couldn't talk?"
"Albus did that on your account," Snape retorted, his calm mask vanishing as he clenched his teeth. "Lupin quite properly reported to him that I'd discovered his secret, and Albus determined that with you in my household, extraordinary measures needed to be taken to protect the truth."
"Oh, that's rich when you're the one Legilimising people on the sly--"
"Yes, and all you do is eavesdrop!" Snape's eyes narrowed. "At the time, I saw Albus' insistence on Fidelius as a lack of faith in me, but considering your own behaviour this evening, perhaps it's more an understanding of your true character."
"True character!"
"Oh, yes," said Snape, his eyes gleaming. "I think of you as Gryffindor more often than not, but that is a misjudgement on my part. You are just as much a Slytherin."
"I am--" In time, Harry realised how silly it would be for him to shout, I am not. He'd be saying it to score points in their argument, not because it was true, or even because he believed it to be. "Yeah, I am."
Feeling a bit embarrassed by then, he looked down, but glanced up through his fringe. "Er . . . are you going to do anything about the eavesdropping, then?"
"Yes. I'll remember it, and ward accordingly."
"And there I thought you were Head of Slytherin," said Draco. "Why didn't you ward your conversation to begin with?"
"It wasn't supposed to be a conversation," growled Snape.
"Oh, sure it was," said Harry. "You wanted Remus to know that you'd found him out. That as good a spy as he ever is, you're better!"
"No, he already knew I'd seen the truth." Snape shook his head.
Maybe so, thought Harry, but you still enjoyed rubbing it in.
"I will say this much, Harry. Lupin . . . surprised me."
"In a good way," said Harry, feeling like he was casting a net, hoping to catch something. Anything. Snape made no reply, though, so Harry pressed a little harder. "I understand about the Fidelius. I do, really. But . . . isn't there anything else you can tell me? Please, Dad?"
Snape regarded him for a long moment, his eyes shadowed. "He isn't worthless, after all."
Once, Harry would have been delighted to hear that. Now, it was like having chocolate snatched away the moment you'd realised it was there. "That's all you can say?"
"Do you suppose it easy to admit that much, and to you, after all I've said about him previously?"
When Harry just waited, Snape blew out a breath. "Very well. One more thing, Harry. I think that Lupin will survive as a deep-cover spy. He does have the necessary . . . skills. But that really is the limit of what I can tell you."