It's only six o'clock in the evening, but he is back, with an ear-to-ear smile.

I stop what I am doing - carving a flute from the Trumpet tree's hollow trunk - and we go and sit in the reclining chairs of the back porch. It rained all day, but now the sky is clear and we can see the sun setting on the horizon. The frogs and toads enjoy themselves in the pools of water, and a cricket starts to sing.

Potter is drinking mango juice and I'm having a cup of Earl Grey. He sums up the day's events by proclaiming that this time it was Luna who saved the day.

Potter, Granger, Ronald and Ginevra Weasley, Longbottom and Lovegood had been flying for hours around Hogwarts in search for Rowena's wand when the peculiar Ravenclaw girl had come up with the idea of using Thestrals, "because Hagrid says they're very good at finding places their riders are looking for". No one had paid attention to her, but she had gone and found a Thestral. Flying on its back, she had ended up finding the wand. While they were discussing how to destroy it, Luna cast bluebell flames on the wand and it burned to ashes.

I gaze at Potter, in awe. I wouldn't believe this tale, if I didn't know his good luck. Then I invite him to have dinner and go to bed earlier, because this time my story will be longer.

"If rumours are true, you went with Dumbledore to the cave where the Dark Lord had hidden Slytherin's locket," I say.

Suddenly, he looks sad. The weather is pleasant and he is under the blankets, but he shivers. "Yes. It was useless, and if we hadn't gone there, the Death Eaters wouldn't have invaded Hogwarts and..." he breaks up and looks at me in terror.

I don't have to read his mind to know what he is thinking. He loathes me. He considers me a murderer, and a coward, and it scares him to realise how close he let me get to him.

"You don't know the whole story, Harry." The name escapes from my lips, and he looks at me, surprised. "Dumbledore's days were already numbered due to the injury sustained from the contact with the cursed Slytherin ring, before the beginning of your sixth term."

"He told me you had stopped the curse."

"Yes, but... he was already dead."

"Dead?"

"Yes. I stoppered his death. Do you remember what I told you in your first Potions class, about a potion to stopper death?"

He widens his eyes, astonished. "You don't want me to believe you can do that, do you?"

"Under certain circumstances, it is possible. Albus was a very powerful wizard, and he had strength to survive in this zombie state for almost a year."

He shakes his head in disbelief. "But... he looked alive."

"And he was, in a way. But he wouldn't have survived much longer."

"In the cave, he made me force him to drink a potion. I don't know whether that potion was poisonous or not."

"How did he react?" I ask, curious.

"He started to have visions, and asked me to stop; then he said it was all his fault, that I had to make it stop, that I shouldn't hurt the other people, that I should kill him instead. He screamed like he was on fire. I had to make him drink twelve goblets, and when he finished the last one, he rolled over into his face. I cast a Rennervate, but at first it didn't seem to work. Then he begged me for water, but the water I conjured with Aguamenti would vanish as soon as it touched his lips. So I plunged the goblet into the cold water of the lake..."

"The lake full of Inferi?"

"Yeah, it was horrible! I tipped the water over his face. Then an Inferius gripped my wrist and tried to pull me into the lake. I cast Petrificus Totalus, Impedimenta, Incarcerous, and even Sectumsempra, but more and more Inferi emerged from the water. Suddenly, a ring of fire appeared, and they did not dare to pass through the flames. I turned to Dumbledore and saw that he was on his feet again, and that the ring of fire was coming from his wand."

"How amazing," I say, in awe. "By drinking that potion, he drank all the sins in the world, ours and his, and after that, he still could find the strength to save you."

"What potion was that?" he asks.

"A potion I would never have been allowed to teach at Hogwarts or anywhere else in the Wizarding World. It's called Nefaserum. It concentrates all the sins and evil that magic can create."

"But the Horcrux that was there was a fake one!" he protests.

"I know. Regulus Black replaced it."

"Sirius's brother? Is he R.A.B.?"

"Yes," I reply. "Regulus Arcturus Black."

"How do you know that? How could he find the cave? And where is the locket?"

"Calm down; I can't answer all those questions at the same time," I complain. " Narcissa Malfoy told me Regulus had stolen the locket. I don't know how he found the cave; I only know he took his house-elf with him."

"Kreacher?"

"Yes, Kreacher."

"Kreacher drank that potion in his place? And he told Narcissa Malfoy? And she told you?"

"Can I continue my story?" I ask him, irked. He looks irked too, as if the name Malfoy was enough to annoy him.

"Yeah."

"Very well. So Dumbledore was alive only due to my potion, which had stoppered his death. Meanwhile, the Dark Lord had given Draco Malfoy the mission to kill the Headmaster. Of course the Dark Lord never believed Draco would be successful; his purpose was to punish the Malfoys. Inadvertently, I found myself forced to make an Unbreakable Vow with Narcissa Malfoy, to keep my cover as a spy."

"I know. You swore to protect Draco."

"Not only that: I swore to fulfil his mission, in case he failed. In these circumstances, Dumbledore made me promise that, if necessary, I would fulfil the Unbreakable Vow."

"He asked you to kill him?"

"In the last instance. He insisted over and over that my position as a spy was crucial to your victory, and that I should earn the Dark Lord's trust."

He gazes at me with an intense look in his eyes. "Damn. He knew what would happen."

A shiver runs down my spine. "This journey through the cave must have debilitated him further. When I arrived at the Astronomy Tower, he was dying. We communicated through Legilimency and he asked me to kill him."

Harry sighs and lowers his eyes. I realise I am thinking of him as 'Harry' now. Perhaps because it is hard to reveal such crucial moments in my life to a person and keep a distant tone.

When he looks up at me, there is a tear glistening in each of his eyes, and he seems so helpless.

I reach out and touch his face, brushing aside an unruly lock of black hair. He holds my hand between his, taking it to his lap.

"The locket is with Narcissa," I tell him. "Regulus didn't know how to destroy it, and left it in Grimmauld Place. He was killed by order of the Dark Lord. A few days before your godfather's death, Kreacher took the locket to Narcissa; in Kreacher's view, the Malfoys are the true descendants of the Blacks."

"And Narcissa didn't give the locket back to Voldemort?"

"No. She is keeping it as a trump card, to make sure the Dark Lord won't hurt anyone in her family. However, if he finds out, all the Malfoys will die before you can say Avada Kedavra, and she knows that. She knows that her family is in danger either way."

"What shall I do?"

"Unfortunately, I think you will have to negotiate with her."

"I'll never convince a Malfoy! Do you have a bottle of Felix Felicis?"

I can't help laughing. "That would be a dirty trick, Harry Potter. And the answer is 'no'."

Harry shakes his head. "I'll never convince a Malfoy of anything," he insists.

"I have a trump card up my sleeve too. But now I'm tired. Let's sleep, shall we?"

He nods, takes off his glasses and settles in his side of the bed. I turn off the lights and lie down. I hear his uneven breath.

"You didn't want to kill Dumbledore," he murmurs.

"That was the last thing I ever wanted to do. He was my mentor. He trusted me. Furthermore, I had a reasonably comfortable life in Hogwarts. My colleagues respected me: Minerva, Filius, Pomona..."

I feel a knot in my throat. It is painful to remember what I have lost.

I am surprised to notice that he is snuggling next to me. I wrap an arm around him, and listen to our hearts beating together.