Wednesday.
The Defense Against the Dark Arts classroom was empty after supper.
This was intentional.
Regulus had checked the schedule twice — Professor Harbinger held office hours on Wednesdays until six, then left for the staff dining room, and the classroom sat unused until the following morning. The door was not locked. It never was. There was nothing in the room worth stealing, unless you counted the collection of Dark object illustrations pinned to the far wall, which Regulus had considered abstractly valuable on exactly one occasion before deciding that abstractly was not a useful category.
He set his bag down on the front desk and stood in the middle of the room.
The Patronus Charm.
He had been circling it for three weeks the way you circled a problem that was not quite a problem yet — examining it from different angles, waiting for the angle that would make it solvable.
The theory was clean. Think of your happiest memory. The happiest you have. Hold it, fill yourself with it, and cast.
The theory was also, in Regulus's experience, the kind of clean that only existed in books.
He had a memory.
That was not the difficulty.
The difficulty was that the memory he had — the one that came when he looked for the word happy and meant it — was small. Unremarkable. Not the kind of thing that felt like it should be sufficient.
He pulled out his wand.
The memory was this:
He was eleven. It was two weeks before Hogwarts, late August, and the house had been in the particular tension of pre-term that he associated with new robes and his mother's careful silences. Sirius had been avoiding every room their father occupied, which meant a complicated choreography of exits and entrances that Regulus had learned to map by sound.
That evening, Sirius had appeared in the doorway of Regulus's room without announcement.
He had a Chocolate Frog in one hand and the expression of someone who wanted company but would deny it if asked.
He had sat on the end of Regulus's bed without asking. Regulus had moved his book. They had not spoken for approximately twenty minutes, which at eleven felt like a reasonable amount of silence.
Then Sirius had said, without any preamble: You know they're going to put us in different houses.
Regulus had said: I know.
Sirius had said: So?
Regulus had thought about it.
Then he had said: So nothing. You'll still be there.
Sirius had not answered. But he had stayed for another hour.
They had shared the Chocolate Frog. Regulus had gotten Merlin. Sirius had gotten Circe, which he wanted more, and had not traded, which Regulus had also not asked him to.
It was not a dramatic memory. Nothing was resolved in it. Sirius had not stopped being difficult, and the house had not stopped being tense, and Hogwarts had sorted them exactly as predicted.
But for one hour in late August, they had been two people in a room who knew something and had found it bearable.
That was the memory.
He held it.
Expecto Patronum.
Silver mist. Faint, thin, dispersing before it formed anything.
He lowered his wand.
The door opened.
Regulus did not turn immediately. He knew the footfall.
"The door was unlocked," Samuel said, by way of explanation.
"I know."
"Lina said you'd gone somewhere with your wand and your thinking face."
"I don't have a thinking face."
"Regulus." A pause. "You have several."
He turned.
Samuel was standing just inside the threshold, bag over one shoulder, in the particular mode he occupied when he had decided to be somewhere without quite announcing that he had decided to be there. He took in the empty room, the wand in Regulus's hand, the silver mist still dissipating in the air between them.
"Patronus?" Samuel said.
"Apparently not."
Samuel came in and sat on a desk near the middle row. Not the front — far enough back to not be beside Regulus, but not far enough away to be absent.
"How long have you been at it?"
"Twenty minutes. Before you arrived."
"And?"
Regulus looked at the dispersed mist. "The mist forms. It doesn't hold."
Samuel was quiet for a moment.
"What memory are you using?"
It was the kind of question Regulus would not answer from most people. He answered it because it was Samuel, and because Samuel asked things in the register of someone who wanted to understand the mechanism, not the sentiment.
"August, two weeks before first year. Sirius came to my room."
Samuel absorbed this without expression. He had learned, over two years, to receive information about Sirius the way you received information about weather: note it, factor it in, do not editorialize.
"Is it actually the happiest?"
Regulus considered.
"It's the most — unambiguous," he said, finally.
"Those aren't the same thing."
"No."
Samuel tilted his head. "The books say happiest, but I've been thinking about that. Flitwick told our year last term that the charm responds to warmth and not to magnitude. That a quiet happy works as well as a dramatic one, if it's genuinely warm."
Regulus looked at him.
"You weren't in our Charms lesson."
"I read the notes. Mira Davies takes very thorough notes." A pause. "The question isn't whether the memory is big enough. The question is whether you're in it when you cast, or standing outside it like it's something you're reporting."
Regulus thought about this.
The memory, when he reached for it: Sirius on the end of the bed. The Chocolate Frog wrapper. The Circe card that Sirius had kept. The specific quality of the silence, which was not comfortable exactly but was chosen — both of them choosing to remain in the room rather than leaving.
He had been holding the memory as a fact.
He had not been inside the part of it that was warm.
He raised his wand.
Expecto Patronum.
The mist formed.
Thicker.
It moved with intention rather than dispersing — gathered itself, reached toward a shape, and then—
A shape.
It held for five seconds, perhaps six, before fading. But it had been there. Silver and deliberate. Small, and low to the ground, and there.
He did not know what animal it was.
It didn't matter yet.
Samuel said, from the middle row, "There it is."
They stayed in the classroom for another forty minutes.
Samuel was not practicing the Patronus Charm. He had a Transfiguration essay due Friday that he was working on at the desk, the scratching of his quill a steady background to Regulus's attempts.
Which was, Regulus recognized, one of Samuel's methods. Not offering help. Not watching with intention. Simply being present while the work was done. It was the same thing he did when Regulus was solving something at the board in their shared study sessions — working on his own thing nearby, available but not looming.
The Patronus formed three more times.
Each time: the same small shape. Low to the ground. Fast-moving, when it moved at all, with a quality of held energy.
On the fourth attempt, it lingered long enough for him to see what it was.
An otter.
He stood looking at it for the full seven seconds it maintained before the silver came apart.
Samuel had looked up from his essay.
"Otter," Regulus said.
"Hm." Samuel considered this with the same equanimity he brought to most things. "That's not what I would have guessed."
"What would you have guessed?"
"Something with more angles."
Regulus looked at the space where the otter had been.
He was not sure what he thought about it. Otters were not—he didn't have a particular relationship with otters. He had not thought of himself as someone whose deepest warmth would produce an otter.
And yet there it was.
"Angles," he said.
"You tend toward straight lines. In how you think. In how you move." Samuel returned to his essay. "An otter is not a straight line."
Regulus thought about the memory. Sirius on the bed. Two weeks before Hogwarts. The particular ease of a silence that didn't require anything.
He thought about this morning. The corridor. You're going to be alone in that house. That's not the same as it being fine.
The otter, he thought, might be less about how he thought and more about what he reached for when he stopped thinking.
He didn't say this to Samuel.
Samuel was writing. His quill had the sound of someone who had returned fully to his own work, which was a form of respect.
Regulus cast again.
The otter appeared immediately this time, silver and specific, and ran a small circle near his feet before dispersing.
He lowered his wand.
"Right," he said, to no one in particular.
In the corner of his vision, Samuel was trying and failing to suppress the expression that meant I told you so in the particular key Samuel used it, which was less triumphant than simply satisfied.
"Don't," Regulus said.
"I didn't say anything."
"You were about to."
"I was going to say," Samuel said mildly, "that Flitwick gives extra marks for demonstrating a corporeal form before we're technically required to."
A pause.
"That's all."
Regulus looked at him for a moment.
Then he picked up his bag.
"Your Transfiguration essay has an error in the third paragraph," he said. "The distinction between Switching and Transformation isn't definitional, it's procedural."
"I know," Samuel said. "I was going to fix it."
"Fix it now."
"Yes, fine." The sound of parchment. "Otter."
Regulus had already reached the door.
"Otter," he agreed, and left.
Lina was waiting in the corridor.
She had a book, which meant she had been waiting for some time, because Lina only brought a book when she expected to wait and wanted no one to feel guilty about it.
She looked at him. He looked at her.
"Otter," she said, before he could speak.
He stopped walking.
"Samuel sent his eagle owl," she said. "It arrived three minutes ago. It just said otter. I didn't know what it meant so I waited."
Regulus considered several responses.
He settled on: "Corporeal Patronus."
Lina's expression moved through surprised, to genuinely pleased, to the particular look she had when she was calibrating whether to make it A Moment or simply let it be a thing that had happened.
She let it be a thing that had happened.
"About time," she said, which was the warmest possible version of not making it A Moment.
"I've been in fifth year for four months."
"I know. I said about time, not past time. There's a difference."
They walked toward the common room.
After a moment, Lina said, "What does the otter mean?"
"Nothing."
"Patronuses always mean something."
"They mean the memory worked."
"Regulus."
He walked for another few steps.
"It means," he said, "that the happiest thing I have is small."
Lina was quiet.
"But sufficient," he added.
She nodded once, as if this were both true and correct and exactly the right amount to say about it.
They went back to the common room.
In the corridor behind them, the Defense Against the Dark Arts classroom was empty again, dark except for the late window light, the silver of the otter already long dispersed.
But the flagstones held the warmth of two people who had been present for something, which was its own kind of record.
It didn't require witnesses.
It had happened anyway.