The Fidelius, the Sacrifice and the Bond of Blood
This time, it was his godfather who followed a bit more reluctantly as Harry walked up to the front door – or rather, what remained of it. It hadn't been repaired after Voldemort had blasted it. Why should it be – there was nothing inside. The house had been cleared out, the furniture and all their possessions sold. The gold now rested safely in Harry's vault at Gringotts.
They entered the hallway, which had gathered an impressive layer of dust. To their left lay the living room, where his father had been playing with him before Voldemort had burst in and killed him, right in this hallway. In fact, Harry might be standing at the very spot where his father's body had fallen.
He turned to the stairs.
"Wait..." Severus' hesitant voice held him back. "Are you sure you really want to go up there?"
He looked slightly pale. Harry suddenly realised how much harder it must be for him to be back here. Harry himself had no conscious memories of the attack. He only knew what he had seen in Voldemort's memories and what people had told him. But Severus...
"You were here that night... I saw it in the memories you gave me in the Shrieking Shack..."
The man he had up to then believed to be his enemy had cradled his mother's body in his arms and had cried – it had been heart-breaking. Harry had never deemed it possible that his cold and disdainful teacher was capable of such emotion.
Severus didn't say anything for a moment. Talking, even thinking about that particular moment was something he always avoided. Harry hadn't been meant to see that particular memory. But when his shields had fallen, he hadn't been able to control the flow of the memories he'd kept locked up behind them for so long. He had just wanted to tell the boy the truth about what had happened and what still remained to be done. And he had wanted him to know that he had always been on their side. But once the dam had broken, everything had gushed out, with his most emotional moments leading the way. He probably would have died of embarrassment about what Harry had captured in those vials if he had known at the time that he'd survive.
"Yes, I was here," he finally said, struggling to find his voice. Coming back here was harder than he had imagined, considering that over 18 years had passed since then.
"Why?" Harry asked, who had paused at the stairway. Voldemort had come alone. He wouldn't have brought the man along who had asked him to spare the life of the woman whose child he was about to kill.
Severus leaned against the wall, obviously seeking support, and briefly closed his eyes. Harry was surprised and oddly moved to see the seemingly impassive, invulnerable man show even such a small gesture of weakness. Contrary to what the majority of people thought to know about him, he was not above human suffering.
"There was a gathering at Malfoy Manor that evening to celebrate the All Hallows feast," Severus began to tell with a halting voice. "The Malfoys were brimming with excitement because the Dark Lord had promised to grace them with his presence. When he failed to show up, however, I had a sense of foreboding."
He had been restless and concerned all day – it was All Hallow, a date the Dark Lord ascribed power to, and just like the year before, Severus had felt the underlying fear that the he might make a strike, even though he had given no such indication, not to him, not to anybody, as far as Severus knew.
"I excused myself from the party, saying that I had to get back to Hogwarts, and apparated straight here. I didn't expected to see anything but an empty house, given that it was under the Fidelius, but while I was standing there, outside the gate, still pondering what to do now and wondering if I was being paranoid, there was flash of green light and the sound of an explosion, and then everything popped into view."
"The Fidelus failed the moment the house was damaged?" Harry sat down on the stairs. He had always wondered about that. The Fidelius charm on Grimmauld Place hadn't been affected by Sirius' death, not even by the death of the Secret Keeper a year later. Hagrid, who had been the first to arrive here, should not have been able to set foot into his parents' house.
"Yes. The Fidelius charm is embedded in the physical structure of the building, while the key to unlock it is hidden in the Secret-Keeper. If the structure is damaged, it damages the spell."
Harry frowned. "But doesn't that make the Fidelius a rather weak protection? Why not simply fire some blasting spells at the hidden building, if a little structural damage is all it takes to bring it into view?"
Severus shook his head. "You didn't listen, Potter. Just like the Unplottable charm, the Fidelius does not simply make a house invisible or place an illusion on it. It literally moves it into a space that is not part of your universe if you haven't been given the key, and replaces it with an alternate reality. Think of Grimmauld Place: There is no empty lot between No. 11 and No. 13. For Muggles and those who don't know the secret, the house simply doesn't exist, even if they know it ought to be right in front of their noses. Death Eaters would only have found an abandoned house on this lot. Even if they had torn it down, it wouldn't have affected the house your parents were residing in. So no, any damage to the building could only have been inflicted from the inside."
Severus had known that he was too late right away. The 'Homo Revelio' he had cast had revealed only one living soul inside the building, and without realising the stupidity of such a move, he had immediately rushed into the house. Had he paused to think about it, he could only have drawn one conclusion: That the Potters were all dead and that the Dark Lord was celebrating his victory inside. But Severus hadn't been capable of rational thinking. He had just reacted. Against all odds, he had hoped...
But just as he had known deep in his gut even before rushing through the broken door, he had found them dead: First Potter right there, near the entrance to the living room, then Lily upstairs. He hadn't even taken notice of the Dark Lord's remains at the wall right behind the open door, where it had been thrown by the backlash of the blast that had made the outer wall collapse.
"You found my mum..."
Severus' impermeable mask fell into place. He avoided Harry's gaze. "I do not wish to talk about it."
The memory of his complete breakdown was a most private one, which nobody should ever have witnessed. Severus had never again given in to sorrow and despair as he had when he had held Lily's dead body in his arms. It was the last time ever he had cried. He had felt as if the world had come to end. Everything he had gone through in the last year... the lies, the spying, the charade... his constant fear of being discovered, the strain of weighing each and every word, of suppressing his every emotion... He had thought it was his penance, the atonement for the guilt that was eating him up inside. He had thought that by protecting her – by protecting them – he could have righted his wrong: Joining the Death Eaters, accepting a vile branding in is skin and making Lily a target. But it had all been for naught. He had failed. Severus had been so devastated that he had not even understood at first that it was all over – that the Dark Lord's power had been broken and that he finally was gone. And even when he had realised it, he had not been able to rejoice about the fact. He had just felt a vast emptiness.
"What about Voldemort?"
"His rather damaged corpse was upstairs, too. We had a hard time making sense of what had happened to him at first."
"We?"
"Dumbledore and I. I sent him my Patronus... as soon as I was able to." He hadn't managed to call upon it at first. As if he'd just been kissed by a Dementor, there were no happy memories left. It was only thanks to his Occlumency shields that he had finally managed to shove it all into a chest and bog in one of the dark sloughs in his mind-scape. And still, for many years after, it had refused to stay under, resurfacing in every moment of weakness and leaking into his consciousness.
"Dumbledore was here?" Harry asked, bemused. "But it was Hagrid who pulled me from the rubble..."
Severus quirked an eyebrow. "You think that Dumbledore, on hearing that your parents and the Dark Lord lay dead in your Fidelius-protected home and that you had mysteriously survived an attack that left part of the house destroyed, wouldn't immediately come to investigate what on Earth had happened, but sent Hagrid, of all people?"
"Well, if you put it like that... I guess it's one of the things I just took at face value and never really thought about. But of course Dumbledore must have wanted to see Voldemort's dead body and not leave him and my parents for Muggles to find. Which begs the question why the place wasn't swarming with Muggles already... One would think that an explosion that brought down an entire wall would have been hard to miss, and with the Fidelius gone the damage must have been visible..."
"No, the Muggle-repellant charm was not only on the house, but on the entire lot and didn't fail. Muggles still saw an abandoned house. Though when the emergency squad of the Department of Magical Accidents and Catastrophes arrived later to deal with the aftermath, they must have made the whole lot Unplottable. The house looks a lot more ramshackle now than it did while it was under the Fidelius charm."
"The house is now Unplottable? So, right now, we can't bee seen by neighbours because we're in a kind of other dimension for them?"
Severus nodded. "I presume the Ministry decided to make it Unplottable because they already suspected it might become a pilgrimage site. Flocks of strangely clad people moving around in the ruin on a regular basis would surely draw attention of Muggles, despite a Notice-Me-Not charm. Besides, there is always the rare Muggle who is immune to it. Unplottability makes sure no one can desecrate the house. Even if the ruin that Muggles see in its stead was torn down, this house would remain untouched."
"I want to go upstairs and see where it happened," said Harry, standing up. He paused. A note of hesitance crept into his voice. "You don't have to... if you don't want to, but..."
He didn't finish the sentence, but his eyes told the entire story. He didn't want to face it alone. Gryffindors! Always so blatantly obvious. Severus pushed himself away from the wall. "Doubtlessly, you're going to have more questions for me. I might just as well answer them upstairs." There wouldn't be much to see. The pictures were all in his head. It didn't matter where he revived them.
They both climbed the stairs. Harry's room was the last on the right. The door was still intact, though withered and warped. The reason became clear when Harry managed to push it open. A part of the opposite exterior wall had collapsed, leaving a hole in the roof and exposing the room to the elements.
Now that he saw everything in front of him, Harry could recall in vivid detail the pictures Severus had bequeathed him with his tears after being near-fatally wounded in the Shrieking Shack. Right there, opposite the door, was where his cot had stood. And here, facing the door, his mother's slain body had lain on the floor. But even though Harry was now seeing the place with his own eyes, it all remained strangely vague – as if it hadn't happened to him. It was probably due to the fact that he had no first hand memories of it. He had only seen it happen through the eyes of other people. Maybe he should be grateful for that.
"What made the wall collapse?" Harry asked. "Avada Kedavra doesn't even leave traces on bodies – I've never heard of it damaging buildings."
"The reverse spell Dumbledore performed on the Dark Lord's wand revealed that he had cast three killing curses. Yet there were only two dead bodies, not counting his own. It was obvious that your parents had been killed with an Avada Kedavra. Given that you were alive and the Dark Lord was dead, the Unforgivable he had cast on you must have been deflected somehow. The brunt of its force must have been diverted around you by some kind of protective shield, and thus directed towards the outer walls behind you, which made them collapse. It looked like the backlash had thrown the Dark Lord into the wall behind him." Severus pointed to a spot behind the door. "This is where we found his body. It was apparent that he hadn't died from the impact, but that the killing curse had rebounded on him – as hard as that was to believe."
"What had happened to his body? I never heard that they found one..."
"The Ministry officials destroyed it. They wanted to make sure that his followers could not try to resurrect him by using Dark Magic and his mortal remains. It was Dumbledore who had pushed for it. He warned them back then that the Dark Lord might return, but of course, no one had taken him seriously. But destroying the body had seemed wise for various reasons."
"Dumbledore had suspected even then that Voldemort would return?" Harry asked, wheels starting to turn in his head. "How would he know? Had he suspected that my scar was a Horcrux?" If that had been the case, he should also have considered the possibility that there might be others, which in turn should have made him start his search into Voldemort's past right there and then. He would have had twelve years to accomplish what Harry, Hermione and Ron had needed to do in just one – finding the remaining Horcruxes and destroying them all. His return could've been prevented.
"I don't think he suspected such a possibility before you started speaking Parseltongue in your second year," said Severus, who had guessed in which direction Harry's thoughts might have drifted. "The knowledge of Horcruxes is not common. But even if he had known, Dumbledore would have kept his suspicions to himself. Who knows what the Ministry would have decided to do about it otherwise? They wouldn't have hesitated to try and destroy it to make sure He wouldn't return – even at the risk of killing you in the process."
Harry didn't seem convinced. "But what else could have made Dumbledore believe that Voldemort was not gone for good?" he asked, a challenge in his tone that was not directed at Severus, but a at the man he had served for fifteen years. While he wished that there might be a logical explanation, he didn't want to be lied to – even at the risk that the perfect image of the great, wise wizard would crack.
"I believe it was the prophesy that made him suspect it: 'And the Dark Lord will mark him as his equal, but he will have power the Dark Lord knows not.' It was just what had happened that night. The Dark Lord had marked you, and thanks to your mother's sacrifice, you now had a power the Dark Lord never understood. And given that the prophesy had proved to be right about that part, I can only assume that Dumbledore was convinced that everything else would also happen as predicted: 'Either must die at the hand of the other, for neither can live while the other survives.'"
Harry frowned. "You said yourself that Voldemort, who only knew the first half of the prophesy, believed that it had already come to pass when he vanished. Why would Dumbledore think differently? Even the second part seemed to have been fulfilled: Voldemort had died at my hands, and I had survived."
Severus shook his head. "On the contrary. The Dark Lord had not died at your hands, but rather at his own. And while you survived, the prophesy claims that he 'cannot live'. But that's rather ominous, isn't it? 'Not being able to live while' is something entirely different from 'being dead'. In fact, the last line seemed to give a clear warning that the Dark Lord's death was not what had occurred that evening. And 'either must die at the hand of the other' clearly indicated a future confrontation. Dumbledore had had about a year's time to study the prophesy and figure out what it might mean for you – he would have concluded that the danger was not over."
Harry wasn't entirely convinced. If Dumbledore had feared that Voldemort might return, it should have made him question how he could have accomplished cheating death. Were there other ways to return except by creating Horcruxes? Lost in thought, Harry left what used to be the nursery and moved down the hallway to look into the other rooms. The one right next to his must have been his parents' bedroom.
"How did Dumbledore know that my mother had sacrificed herself in the first place?" Harry inquired, intent on getting to the bottom of things. Severus had remained in the hallway, silently watching Harry as he moved around. "It sounds like a lot of guesswork."
"You had traces of an ancient protective magic all over you – sacrificial magic. We had a good idea what had happened even before Dumbledore went into your mind to witness the events through your eyes. As children have no shields, using Legilimency on them is easy and painless, but the memories are a bit fuzzy if not viewed in a Pensieve. But what he saw in your memory confirmed his guess: That Lily, in sacrificing herself for you, protected you from the killing curse, making it rebound on Voldemort instead."
So Dumbledore had used Legilimency on him... Under the circumstances, Harry couldn't blame him for that. Had he deleted Harry's memories afterwards or had they simply faded with time? Harry didn't have any pictures in his mind that showed his mom standing protectively in front of him and refusing to step aside. All he remembered was her scream and the flash of green light. "I never really understood how that spell worked..." he muttered. "Voldemort not being able to touch or kill me because she died in my stead – it sounded pretty esoteric to me. "
"It's not a spell," Severus corrected. "The protection is brought about by an act of will. Lily consciously gave her life to protect yours after having been given a choice. The Dark Lord, so it seemed, had kept the promise he made to me and had offered to spare her life, which enabled her sacrifice. It would have remained a one-time occurrence, if Dumbledore had not recognized the ancient magic that was at work here and took the chance to cement it with a blood bonding charm he cast on you."
"He used blood magic on me?" Harry asked, aghast.
"No, not blood magic, Potter, as that requires the spilling of blood and is therefore considered a Dark Art. The 'Bond of Blood' is basically a magical adoption. It made it possible for Dumbledore to extend the sacrificial protection and anchor it in your aunt."
That explanation was even more shocking. "I was magically adopted by my aunt?" Harry's eyes went wide.
"As little as you might like it, yes. She was the only person in whom the maternal protection evoked by Lily's sacrifice could be bound, as Petunia shared your mother's blood. By accepting guardianship, accepting a mother's responsibility – to give you a home, to give you shelter, to protect you – Petunia took your mother's place. As long as you were a minor in her care, Lily's protection persisted."
Harry snorted. "My aunt never acted as my mother. She never even considered me family."
"She must have," Severus objected. "Otherwise the magic wouldn't have taken hold. I know Petunia. She had always been jealous of her sister, but she had also loved her. She just had come to hate everything that set Lily and her apart. Dumbledore explained everything to her in a letter, making it very clear that by taking you in, by stepping into your mother's place, she gave you a strong protection against the one who had killed her sister. She could have refused, and Lily's sacrifice would have remained a one-time salvation, the Bond of Blood would never have activated. But she didn't."
Was it true? Had Petunia taken him in out of love and loyalty for her sister? Had she been fully aware of the fact that she was saving his life by doing so? But why save it only to make it miserable?
Severus sounded bitter when, unwittingly, he answered Harry's silent question: "What Dumbledore with all his rambling about love failed to understand, is that loving someone doesn't necessarily equal treating him decently." One could love and hate someone with equal measure. Severus had seen it with his parents. And in a certain way, he had experienced it himself in his relationship with Dumbledore. "Petunia had loved Lily, but she was still mean and spiteful to her. Why should she treat you differently? Giving you food and shelter was enough to fulfil her primary obligation of a parent. Love was not a requirement."
Once again, Harry could only shake his head at the irony of it all. With Petunia and Severus, he had had two people in his life who had obviously gone to all the bother of protecting him, but still had strongly disliked him and treated him like shite. Though at least with his godfather, he became more and more hopeful there was a way to better this relationship.
"So I had to go back to the Dursleys once a year just so that Petunia could sort of act in my mother's stead by giving me food and shelter..." Harry resumed, wishing someone had bothered to explain it back then. Dumbledore had presumed too much – had somehow forgotten that Harry had not been born into the wizarding world and had no inherent understanding for these concepts. But then he doubted that Ron would have understood any better. Dumbledore had often cloaked his wisdom in mystery.
"Yes," Severus confirmed, exhibiting a lot more patience that Harry would have ever given him credit for. "Only while you were a child in her care, the Dark Lord literally could not touch you. His magic did not work properly against you."
Harry wondered what might have happened if Voldemort had tried to kill him with non-magical means and without touching him – like a gun. Would the magical protection have recognized it as an extension of his hands? It was probably a good thing that the idea never crossed his mind.
He opened the next door. A bathroom. He was glad that someone had emptied the house. He had no idea how he would have felt if he had found toothbrushes, a hairbrush or half-empty shampoo bottles standing around.
"What some considered sheer dumb luck when you escaped him again and again, was your mother's protective magic hovering over you," Severus said, qualifying his statement by adding: "Well, that, and a few added perks, like the brother's wand and the fact that the Dursleys' house was basically Unplottable to Voldemort."
"Aunt Petunia's and Uncle Vernon's house was made Unplottable?"
"No, this particular charm works only against Muggles. If you wish to hide something magically from wizards, your only means is the Fidelius charm. Obviously, they couldn't do it with the Dursleys' house. But it wasn't necessary. The protection of your mother made sure that in your home, were her blood dwelled, you couldn't be harmed by him. From what I understood, the Dark Lord was unable to even locate the place."
Harry frowned. "What about his Death Eaters?"
"I know for sure that he sent them after you in the summer after his return. But they were unable to find even the street. The ended up roaming the neighbourhood without ever getting close to Privet Drive. It's as if it didn't exist. I don't know if it was an exceptionally strong Confundus charm, or if somehow, the entire street had become Unplottable to the Dark Lord and those who acted on his orders. But it kept him away. That's why he arranged for the Dementors."
"It looks like they couldn't find Privet Drive, either," Harry said. "They got me a few blocks down from there, in Magnolia Crescent."
"Which is why Dumbledore had you brought to Grimmauld Place. He wasn't entirely sure how much the fact that the Dark Lord had taken your blood for his resurrection had affected the magical protection your mother had given you."
"When he used my blood to create his new body... it changed something. After that, he was able to touch me. But Dumbledore still was oddly elated when I told him what Voldemort had done."
"Yes, because by doing so, unknowingly and quite unintentionally, the Dark Lord gave you the ultimate protection. Without his intervention, your mother's protection would have faded once you reached maturity, but by taking your blood into himself while the protective magic was still bound in it, he made himself a vessel. He became your Horcrux."
"What?" choked Harry, and his mouth fell open in shock.
"Well, maybe I should call it a reverse Horcrux, because in many ways, it was an exact antithesis," Severus toned down his outrageous statement. "Although the result was similar: Your mother's protection in his blood tethered you to this plane just like a Horcrux would have, at least as long as it was the Dark Lord who tried to kill you. The creation process, however, is the exact opposite. When creating a Horcrux, you must take another person's life with the intention of preventing your own death. For sacrificial protection, you must give your own life with the intention of preventing the death of another. When Voldemort created his Horcruxes, he tore pieces from his soul and diminished in the process. When your mother sacrificed herself for you, a part of her – her magical protection – stayed with you and strengthened you. Both, the soul pieces and the sacrificial protection, need a vessel outside of your own body to persist. Petunia became an anchor for your mother's magic, but it was bound to her role rather than her blood and was thus only temporary. The Dark Lord literally took your blood – Lily's blood – into himself. By doing so, he made sure that the protective magic that prevented him from killing you lived on in his body. The rather absurd consequence was this: As long as he lived, he could not kill you. And because of his Horcrux inside you, you could not kill him while you lived."
"Neither could die at the hand of the other while the other survived," murmured Harry, wondering if it was the same or the exact opposite to what the prophesy claimed. But then, he had never fully understood that line anyway. "But I wasn't immortal. And Voldemort did kill me in the end."
"Not really. You sacrificed yourself. And because of your mother's protection, you were given a choice. Your soul was able to return into your body, which is more than the Dark Lord had achieved with his Horcruxes. When he died while they still existed, his soul was bound to this Earth, but it didn't have a physical body anymore. Surely a major flaw in his plans to achieve immortality."
Yes, doubtlessly so. Harry briefly wondered what would have happened if Voldemort had incinerated his body after casting his 'Avada Kedarvra', leaving his soul no vessel to return to. Would he have remained behind like Voldemort had – less than a ghost, a whip of smoke? He'd rather not think about it. He'd have preferred death over such a form of existence.
Harry opened the door to the last room on this floor. A spare bedroom. Had they planned for another child? Would he have had brother and sisters, if they had lived? He knew so little about their lives and their dreams. Finding nothing here that could tell him more about them, Harry made for the stairs again.
The Potters' house
The current condition of the Potter cottage is a bit hard to determine. In 'Deathly Hollows' (book), when Hermione and Harry are looking at the cottage, they see that
"most of the cottage was still standing, (...), but the right side of the top floor had been blown apart (...) where the curse had backfired."
"His touch on the gate seemed to have done it. A sign had risen out of the ground in front of them (...) 'This house, invisible to Muggles, has been left in its ruined state as a monument..'"
In the movie, however, when Hermione and Harry are standing in front of the building, the entire upper floor is a wreck, the roof basically gone. They also never touched the gate.
In Deathly Hallows , we see Severus approaching the house in the night of Halloween, in which the house is slightly damaged.
To create a logical consistency, I'm assuming the following:
The first muggle repellant charm that was cast placed an illusion on the building, showing it abandoned to Muggles and Wizards alike (as long as the latter didn't touch the gate). It was supposed to support the rumour that the Potters had moved away, while in truth, they were still living there in hiding.
When the Fidelius was cast, it moved the house into a different dimension for wizards and Muggles alike, exchanging it with a 'replacement building': an empty and now slightly damaged house, just like what Snape saw when he arrived in Godric's Hollow shortly before Voldemort cast the killing curse and shortly before the Fidelius fell. (I'm just assuming here that the String theory about multiverses holds true and that it would have been easy to find a fitting replacement building in one of the other dimensions. :) How's that supposed to work? Don't know. :) It's magic!)
In the aftermath of the Halloween attack, the Ministry Task Force team made the entire lot unplottable to Muggles and created a 'virtual reality building' that looked utterly ruined. (Either to nip any Muggle's idea to rebuild it in the bud or because they simply can't do anything but ruins for a replacement. After all, a ruin is what Muggles see when they look at Hogwarts.) This is what Hermione and Harry saw when approaching the house, but before touching the gate (which was never shown in the movie)
The Potters 'in hiding'
We are told that the Potters were in hiding long before the Fidelius was cast, though it isn't explained what exactly that means. We know that for Christmas 1980, Petunia somehow sends 'a fugly vase' to Lily for Christmas. As Petunia would hardly have used an owl, it must have been delivered by regular mail, which means that Petunia obviously knew their address and the house must have still been visible to the Muggle mailman at that point.
Since hiding normally means 'being where no one can see you' and 'no one knows where you are', something must have happened to the Potters and their house in between Christmas 1980 and Fall 1981, when it was put under the Fidelius and really hidden from the rest of the world.
Making it seem as if they had moved away while hiding them in a house that was made to look abandoned was the only logical explanation I could come up with.
Voldemort's body
There's more to this question than one would think. Was there a body? There had to be! For one, because Avada Kedavra does not cause physical damage. It's weird enough that the wall collapsed when his curse backfired. But if had pulverised his body, neither the house, nor Harry or Voldemort's wand should have survived the destruction.
The second reason is this: Without the proof of a body, how could the ministry people have been so convinced of Voldemort's death that the Daily Prophet proclaimed it and people celebrated in the streets?
There was scant evidence for his demise: Priori Intantatem could only have revealed that three Avadas had been cast with this wand. Added to that, there were two victims, a destroyed wall and a lost child, the absence of which Dumbledore would have had to explain later. The ministry people never even saw Harry! I fail to understand how they could have come to the conclusion that Harry survived an Avada Kedavra.
So if we presume that the ministry people must have seen the body in order to deduce that an Avada had backfired and killed the Dark Lord, Harry was absolutely right to wonder why Dumbledore was so sure that he would be back. Because of the prophesy? Or did Dumbledore in deed have suspicions regarding Harry's very prominent scar? Either way, he should have drawn the conclusion that Voldemort must have created Horcruxes, for as far as we know, there is no other way to return once you're dead.
The 'Bond of Blood'
The fact that Dumbledore puts this charm on Harry to extend his mother's protection is the best proof I have for my claim that Dumbledore must have been in Godric's Hallow with Harry before meeting him again at Privet Drive the following night, as he never casts a charm on him while there.
I tried to stay as close as possible to this explanation on the Harry Potter Wiki: The sacrifice creates a lingering protection in the blood of the person who was saved. It is not activated, however, until the (Bond of Blood) charm is actually cast, and it is not sealed and functioning until another member of the family accepts the saved person as his or her own."