"I've been thinking about it," Harry said. "I'll do it, but there are five conditions -"
"Five?"
"Yes, five. Look, Draco, a pledge like this is just begging to go terribly wrong somehow, you know it would go wrong if this were a play -"
"Well, it's not!" Draco said. "Dumbledore killed Mother. He's evil. It's one of those things you talk about that doesn't have to be complicated."
"Draco," Harry said, his voice careful, "all I know is that you say that Lucius says that Dumbledore says he killed Narcissa. To believe that unquestioningly, I have to trust you and Lucius and Dumbledore. So like I said, there are conditions. The first one is that at any point you can release me from the pledge, if it no longer seems like a good idea. It has to be a deliberate and intended decision on your part, of course, not a trick of wording or something."
"Okay," said Draco. That sounded safe enough.
"Condition two is that I'm pledging to take as an enemy whoever actually did kill Narcissa, as determined to the honest best of my ability as a rationalist. Whether that's Dumbledore, or someone else. And you have my word that I'll exercise my best ability as a rationalist to keep that judgment honest, as a question of simple fact. Agreed?"
"I don't like it," said Draco. He didn't, the whole point was to make sure Harry never went with Dumbledore. Still, if Harry was honest, he'd catch on to Dumbledore soon enough; and if dishonest, he'd already broken his word... "But I'll agree."
"Condition three is that Narcissa has to have been burned alive. If that part of the story turns out to be something exaggerated just to make it sound a little worse, then I get to decide for myself whether or not to still go through with the pledge. Good people sometimes have to kill. But they don't ever torture people to death. It's because Narcissa was burned alive that I know whoever did that was evil."
Draco kept his temper, barely.
"Condition four is that if Narcissa got her own hands dirty, and, say, Crucioed someone's child into insanity, and that person burned Narcissa for revenge, the deal might be off again. Because then it was still wrong for them to burn her, they still should've just killed her without pain; but it wasn't evil the same way as if she was just Lucius's love who never did anything herself, like you said. Condition five is that if whoever killed Narcissa was tricked somehow into doing it, then my enemy is whoever tricked them, not the person who was tricked."
"All this really sounds like you're planning to weasel out of it -"
"Draco, I won't take a good person as an enemy, not for you or anyone. I have to really believe they're in the wrong. But I've thought about it, and it seems to me that if Narcissa didn't do any evil with her own hands, just fell in love with Lucius and chose to stay his wife, then whoever burned her alive in her own bedroom isn't likely to be a good guy. And I'll pledge to take as my enemy whoever made that happen, whether it's Dumbledore or anyone else, unless you deliberately release me from that pledge. Hopefully that won't go wrong the way it would if this were a play."
"I'm not happy," said Draco. "But okay. You pledge to take my mother's murderer as your enemy, and I'll -"
Harry waited, with a patient look on his face, while Draco tried to make his voice work again.
"I'll help you fix the problem with Slytherin House hating Muggleborns," Draco finished in a whisper. "And I'll say it was sad that Lily Potter died."
"So be it," said Harry.
And it was done.
The break, Draco knew, had just widened a little more. No, not a little, a lot. There was a sensation of drifting away, of being lost, further and further from shore, further and further from home...
"Excuse me," Draco said. He turned away from Harry, and then tried to calm himself, he had to do this test, and he didn't want to fail it from being nervous or ashamed.
Draco raised his wand into the starting position for the Patronus Charm.
Remembered falling from his broomstick, the pain, the fear, imagined it coming from a tall figure in a cloak, looking like a dead thing left in water.
And then Draco closed his eyes, the better to remember Father holding his small, cold hands in his own warm strength.
Don't be frightened, my son, I'm here...
The wand swung up in a broad brandish, to drive the fear away, and Draco was surprised at the strength of it; and he remembered in that moment that Father wasn't lost, would never be lost, would always be there and strong in his own person, no matter what happened to Draco, and his voice cried, "Expecto Patronum!"
Draco opened his eyes.
A shining snake looked back at him, no less bright than before.
Behind him, he heard Harry exhale a breath, as though in relief.
Draco gazed into the white light. It seemed he wasn't lost completely, after all.
"That reminds me," said Harry after a while. "Can we test my hypothesis about how to use a Patronus to send messages?"
"Is it going to surprise me?" said Draco. "I don't want any more surprises today."
Harry had claimed that the idea wasn't all that strange and he didn't see how it could possibly shock Draco in any way, which made Draco feel even more nervous, somehow; but Draco could see how important it was to have a way of sending messages in emergencies.
The trick - or so Harry hypothesized - was wanting to spread the good news, wanting the recipient to know the truth of whatever happy thought you'd used to cast the Patronus Charm. Only instead of telling the recipient in words, the Patronus itself was the message. By wanting them to see that, the Patronus would go to them.
"Tell Harry," said Draco to the luminous snake, even though Harry was standing only a few paces away on the other side of the room, "to, um, beware the green monkey," this being a sign from a play Draco had once seen.
And then, just like at King's Cross station, Draco wanted Harry to know that Father had always cared for him; only this time he didn't try to say it in words, but wanted to say it with the happy thought itself.
The bright snake slithered across the room, looking more like it was slithering through the air rather than the stone itself; it got to Harry after traveling that short distance -
- and said to Harry, in a strange voice that Draco recognized as how he himself probably sounded to other people, "Beware the green monkey."
"Hsssss ssss sshsshssss," said Harry.
The snake slithered back across the floor to Draco.
"Harry says the message is received and acknowledged," said the shining Blue Krait in Draco's voice.
"Huh," Harry said. "Talking to Patronuses feels odd."
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"Why are you looking at me like that?" said the Heir of Slytherin.
Aftermath:
Harry stared at Draco.
"You mean just magical snakes, right?"
"N-no," said Draco. He was looking rather pale, and was still stammering, but had at least stopped the incoherent noises he'd been making earlier. "You're a Parselmouth, you can speak Parseltongue, it's the language of all snakes everywhere. You can understand any snake when it talks, and they can understand when you talk to them... Harry, you can't possibly believe you were Sorted into Ravenclaw! You're the Heir of Slytherin!"
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"SNAKES ARE SENTIENT?"
Chapter 48: Utilitarian Priorities