Krum, pale white over the dirty white of his prison uniform, stood in the faint light of the prison cell. The beam of light protecting Ron and Harry from him seemed all too thin, all too weak.

As if sensing their discomfort, he reached forth one of his unnaturally elongated fingers until it touched the light. There was a sizzle, a trail of smoke, and he yanked his hand back. He hissed in pain and sucked the fingertip. Harry was surprised he didn't hurt himself with those shark teeth of his.

"Was it you?" Harry said.

"Was it I what?" Krum said, still looking at his hand.

"You know what," Ron said. "Did you attack Harry? Answer the question."

Krum's glowing, yellow gaze turned to Ron.

"And how is Hermio-ninny, Ronald?" Ron said nothing.

"I understand she fought my extradition."

Ron frowned sympathetically. "Yeah, well, she tried. Really tried. Wore herself out. Arguing, writing world leaders, bargaining. Didn't work. Rules are rules. Treaties are treaties."

Krum made a nasty smile. "I must have been a good lover for her to try so hard, yes?"

Ron drew his wand and took a step forward. Harry grabbed him and pushed him back against the far wall.

"Stop it Ron," he said. "He's just trying to bait you into crossing the light."

Ron took a deep breath and nodded. Harry let him go. Krum laughed.

"Ah, Ronald, you need not worry. Back in school, during the tournament, we kissed two times. Each time, she would talk about you afterwards. I was never competition. She loves you. Always has."

Ron said nothing, but Harry felt him relax. He stopped pinning him against the wall.

"Can we stop, now?" Harry said, scowling at Krum. "Can we get to the reason I'm here?"

Krum turned to look at Harry. He took a deep, long breath through his nose. Then he let it out slowly. He smiled.

"Harry, you are accursed. Yes?"

"Yes. An injury," he said and gestured to the scar on his cheek. "Followed by damage to my memory."

Krum nodded. "Multiple layers. Very difficult magic. Very powerful."

"I can't remember who attacked me or why. I just know they were trying to hurt me. Was it you?"

Krum went back to the far side of the room. There was a cot against the wall. He sat down and stared at the two of them. The darkness that seemed to obey him didn't return. In the dim light, he looked weak

"I am become vampire on purpose, you know that?" he said.

Harry nodded. He'd heard but hadn't believed. Why would anyone volunteer to become a monster?

"Do you know why?"

"Because, with your accent, all you need is a cape and your Dracula Halloween costume is complete?" Ron said.

Krum didn't laugh.

"I wanted something. Needed. There was a great wrong done. To me. To someone I loved. I wanted to correct this wrong. Revenge myself. But those people - those beasts - I could not get to. They had friends. Connections. I was not powerful enough. To become a beast myself, this was the only power within my reach."

"And did you?" Harry said. "Did you get your revenge?"

Krum leaned back against the wall and shook his head. "I understand you. I understand your frustration, your rage. You want to revenge yourself on the one who murdered your wife."

"Was it you?" Harry asked, already knowing the answer.

"No," Krum said. "Have you come here so I might turn you to vampire?"

"No," Harry said.

He felt Ron relax slightly beside him.

"This curse of yours. I am not powerful enough for this," Krum said. "I am sad to say it is beyond even my ability."

"Do you know who could have done it?" Harry said.

"Who could have done it?" Krum said. "Not many. It takes a power that is not normally attainable by humans. You must steal eldritch wizardry from a greater power. Who could have done it? Your Voldemort, perhaps. Grindlewald." He tilted his head, side to side as if reconsidering. "Dumbledore, although he would never dare."

"Anyone alive?"

Krum let out a low chuckle. He stroked his face with long fingers. He smiled.

"You want something from me. Yes? You want the name of someone who could have done this. What do you have to offer me in return?"

"Just a minute ago you said you two were friends," Ron said.

Krum made a noncommittal noise. "I said 'friendly.'"

"I have money," Harry said.

"Bah. I have no use for money anymore."

"I don't have anything else to trade," Harry said. "I can't stop your extradition. I can't break you out of here. I can't cure your vampirism. What do you want?"

Krum didn't seem to move. He didn't get up and walk closer to them. He was just there. There wasn't even a flicker of movement. He was just standing across the sunlight from them. Krum stared at Harry, smiling with those horrid teeth.

"Blood," Krum said.

"Not going to happen," Ron said. "We give you blood, you have enough power to break out of here."

Krum sank back into the darkness, making a sad whimper.

"Wouldn't take much. Just a taste. You could reach your arm through the light. I bite your wrist. Just a taste. You could pull right back. I haven't had blood in so long."

Harry said nothing.

"You said you wanted my help," Krum said. "You said you wanted to know your attacker, who killed your wife. This is the price. If you are not willing, go home and make peace with it."

"Fine," Harry said. "I'll do it."

"You can't be serious!" Ron said, stepping between them.

"We are agreed?" Krum said, trying to look around Ron. "Information for blood?"

"Just a little," Harry said. "Not enough to escape. Promise me."

Ron grabbed his shoulders. "You can't trust him. He's a vampire."

Krum was back on his feet, standing proudly, arrogantly, near the light.

"I do not lie. I do not break agreements. I promise you I will take very little."

"It's a deal," Harry said, pushing Ron aside. "Now tell me who attacked me."

"You were not attacked," Krum said.

Ron held up his arms, staring at Harry with an exaggerated I-told-you-so expression.

"I know I was attacked," Harry said, pointing to his cheek. "Two-layer spell, remember?"

Krum shook his head. "You weren't attacked by a multi-layer spell because nobody attacks with a multi-layer spell. Do you even know how they work?"

Harry and Ron stared at each other a moment. They did not. Almost no one did. Harry hadn't found much information on layered spells in all his research. He'd even gone through every possible source at the Hogwarts library, driving the reference librarians insane.

"Then explain," Harry said.

"Each layer adds an order of magnitude to complexity and casting time. Let me explain. Give me… Give me an example of a curse."

"Tarantallegra," Ron said immediately. It was one of the curses he hated most back from their days at school.

"Tarantallegra," Krum said, waving his hand in the air as if he was casting the spell with a wand. "It takes, what, four seconds to cast? Let us say six to make easy math. Now, another spell, please."

"Expelliarmus," Harry said.

"Yes. Good. Now, this is how you would cast those two spells as multiple layers," Krum said, raising his hands again. "Tar. Expelliarmus. Ran. Expelliarmus. Tal. Expelliarmus. Leg. Expelliarmus. Gra. Expelliarmus. You see?"

"You have to cast the second spell with each syllable of the first," Harry said.

"Yes, and the wand movements must do the same. Very complex patterns. Very bad if you get even a tiny bit wrong."

"Then a third level would be even harder."

"Yes. Layer upon layer. So, if the first spell took six seconds, adding a layer would make casting it take 60 seconds. A third layer would be 600 seconds. And so on. This is why I know you were not attacked. In a fight, your opponent would not take so much uninterrupted time to strike you."

"Then…" Harry said, his mind turning to dark places he didn't want to go. "Then I wasn't…"

"You were simply in the wrong place at the wrong time."

"Isn't that what you told your victims?" Ron said, darkly.

"Some of them," Krum said, smiling.

"Whoever did it," Ron said. "They could have been preparing the spell ahead of time. Maybe they knew Harry was coming."

Krum shook his head, smiling like a teacher showing off how much more he knew than his students.

"Much more effective casting spells separately. No? Two curses are faster than a two-layer curse. Why would anyone ever do multi-layer spell?"

"Why don't you just tell us?" Harry said, crossing his arms. "Instead of all this Socratic crap."

"Multi-layer spells are useful if you want to combine some aspect of each spell into something new. In our example, the spell might make someone dance and drop a wand with every step."

"That doesn't make any sense," Ron said. "Nobody carries more than one wand."

"It's just an example," Krum said. "Say we reverse the layers. It makes you drop your wand and anyone who picked it up would dance."

"Nobody would want that, either."

Krum made a frustrated noise. "Fine. You cast the floral scent charm as first layer. Second layer is the death curse. Anyone who smells flowers dies. Good way to kill anyone who enters a room."

"So," Harry said slowly, "I wasn't attacked on purpose. I walked in on someone casting a complicated spell and just… Got in the way."

Krum nodded. Harry frowned. Embarrassment grew in him. He wasn't the crusading auror he thought he was. He'd blundered into something like an idiot. Like Mulciber said he was.

"Thank you, Viktor," he said.

Krum bowed in salute, adding a flourish with one, unnaturally-long fingered hand.

"We better go, mate," Ron said, steering him towards the door and knocking on it. "Time's almost up."

Krum made tiny whining noises. It reminded Harry of Peter Pettigrew.

"But we had deal, Harry. You promised."

Harry brushed Ron's hand off.

"Harry, you can't be serious!" The door squealed open.

"I made a deal," Harry said.

Ron shook his head at the opened door. It squeaked close.

"Here," Harry said, holding out his wand. "Cover me."

Ron took it, frowning, then drew his own wand and pointed it straight at Krum.

Harry stepped towards the jagged line of sunlight and reached an arm slowly across. Krum gingerly pulled Harry's sleeve back with his right hand, revealing his wrist. With his other hand, Krum enfolded Harry's. The fingers were cold and dry. Krum looked down at Harry's wrist, at the pulsing vein, as if looking at a lover. He took a deep inhalation through his nose, sensing an aroma beyond what a human could smell.

"Thank you for this kindness, Harry. We are more than friendly. For the rest of my days, few as they will be, I will consider you my good friend."

With a quick, unnaturally powerful motion, he dragged Harry across the beam of light.