A short, incomplete recap: The major secret, and trick, in the book is that Dumbledore does not appear in the book. He is played by someone using Polyjuice, most likely Wormtail. I give many many proofs for this in the previous post, so read that post for more details. Examples: in Slugworn's house, Dumbledore suddely straightens up and excuses himself to use the bathroom. This was because the Polyjuice was wearing off. Dumbledore was not expected by Mrs. Weasley until morning. A big deal is made of Mrs. Weasley not checking if people entering her house (and this explicitly = Dumbledore and Tonks) are not Death Eaters. In the cave, Dumbledore has the strength of "a much younger man." Dumbledore's right hand is shriveled, just as Wormtail cut off his right hand in an earlier book for a potion for Voldemort, one replaced with a silver one. Dumbledore wears a satisfied expression that Harry's scar does not hurt, a sign that Voldemort is successfully blocking off Harry. Dumbledore says that he might not be Dumbledore but rather a Death Eater. Dumbledore understands Parseltongue, which Dumbledore says was a worrying sign in the young Voldemort. Dumbledore wants Harry to tell his friends the prophecy, perhaps to increase chances that he find out about it. Dumbledore only mentions details of the prophecy after Harry mentions them. Dumbledore's muttered words in the cave are not directed at Harry but refer to an earlier event. Snape's look of hatred and disgust, which we would not expect directed at Dumbledore. In explanation of the meaning of the sessions with Harry, Dumbledore seems to be extracting information from Harry about the prophecy. Etcetera.
Further, Tonks also seems to be in on the conspiracy, and is perhaps also someone using Polyjuice. Multiple times, she appears literally out of nowhere just as Harry is about to discover something major and throws him off track. E.g. when he is about to follow Mundungus, or when he is waiting outside the Room of Requirement to catch Draco Malfoy. The book, in fact, mentions that the looks like Malfoy - "Was it his imagination, or did Draco, like Tonks, look thinner?" She leaves right after Dumbledore arrives at the Weasley's, and Dumbledore appears to follow her. Her Patronus is different than her usual one, because she is a different person. Etcetera. Read the previous post for more details.
Further, number 12 Grimmauld Place is in the hands of Bellatrix Lestrane and Voldemort's supporters. The "proof" of Kreacher's following Harry's command is no proof. He would be compelled to do the same had been inherited by Bellatrix and been ordered to follow Harry's command. If Kreacher is in Bellatrix's hands, he spilled all the beans about the Order, which is bad news. The Order of the Phoenix moved out of the place because it is in the hands of Bellatrix. Mundungus is seen by Harry selling items from the house, which he stole, but not from the Order or from Harry, but from Bellatrix. Harry was about to investigate this when Tonks appears out of nowhere and dissuades him.
I discuss more in the previous post, but that is the basis we need in order to proceed.
Why does Dumbledore freeze Harry under the cloak at the very end? The entire scene is a put-on, to feed Harry false information. Harry is to see Dumbledore "killed" by Snape, to get an "explanation" of what Draco Malfoy had been trying to accomplish, what Draco had tried to get fixed, why he had tried to send the cursed necklace into Hogwarts, to get information about the identity of the half-blood prince. Do not trust most of what plays out in this scene, since it is deliberate misdirection.
Why not begin with the locket, one of the seven Horcruxes.
A. The Locket
When going with Harry to fetch the locket, Dumbledore knows exactly where to go and what to do. It even looks to Harry like Dumbledore is not performing magic, but dismisses this as a sign of Dumbledore's expertise. In fact, the author is writing this to hint that no magic is being used. They get the locket, which at the end appears by Dumbledore's body, having fallen from his pocket. Inside is a piece of parchment with the following note:
To the Dark LordR.A.B. is Rigelus Black, Sirius' brother. In a previous book, Harry had encountered a locket at number 12 Grimmauld Place that he was unable to open. This was the true Horcrux. Thus, Voldemort et. al. were already in possession of it, since they were in possession of number 12 Grimmauld Place. The whole quest in the cave was a put-on, for "Dumbledore" already knew where the true locket was. Alternatively, Mundungus was sent by the Order to steal many items from the Black's residence, including the locket, so that they would not know which stolen item was the Horcrux (They = the bad guys only find out it is the locket from the Pensieve.) That is why Mundungus was selling off multiple items.
I now I will be dead long before you read this but I want you to know that it was I who dicovered your secret. I have stolen the real Horcrux and intend to destroy it as soon as I can.
I face death in the hope that when you meet your match you will be mortal once more.
B. The Opal Necklace
This was given to Katie Bell, who was to deliver it to Hogwarts. As we "find out" in the scene in which Draco confronts Dumbledore, this was given by Draco in an attempt to kill Dumbledore. Harry argues as much earlier, but this idea is dismissed out of hand by Ron, Hermione, and Professor McGonagall. Let us consider the close of the chapter, a discussion between the three friends:
"It wasn't a very slick attack, really, when you stop and think about it," said Ron, casually turfing a first year out of one of the good armchairs by the fire so that he could sit down. "The curse didn't even make it into the castle. Not what you'd call foolproof."JK Rowling is giving us a big hint. It was not a very slick attack. As we read earlier, everyone was getting scanned by Filch as they entered Hogwarts. How did Draco plan on getting it in to the castle, even had Katie Bell not been affected and had Harry and company not gotten hold of the necklace?
"You're right," said Hermione, prodding Ron out of the chair with her foot and offering it to the first year again. "It wasn't very well thought-out at all."
"But since when has Malfoy been one of the world's great thinkers?" asked Harry.
Neither Ron nor Hermione answered him.
"Hagrid says you four saw what happened to Katie Bell ... upstairs to my office at once, please! What's that you're holding, Potter?"So the necklace would have been discovered anyway, and would not have made it into Hogwarts. Instead, what happens is that the necklace is brought to Hogwarts, by an unwitting Harry Potter and friends, and Filch is sent with the necklace to bring to Snape! Draco's plan, if it was his plan, is absolutely brilliant. Of course, it requires "Professor McGonagall" to be in on it, but then, she is the one who gives Draco his alibi (detention). Perhaps this necklace was indeed what Draco brought with him to the shop of Borgin and Burkes, rather than the cabinets, Hermione's dismissal of the idea aside.
"It's the thing she touched," said Harry.
"Good lord," said Professor McGonagall, looking alarmed as she took the necklace from Harry. "No, no, Filch, they're with me!" she added hastily, as Filch came shuffling eagerly across the entrance hall holding his Secrecy Sensor aloft. "Take this necklace to Professor Snape at once, but be sure not to touch it, keep it wrapped in the scarf!"
(How then, did the Death Eaters enter Hogwarts? We see from the Apparating classes that "Dumbledore" has the ability to relax the spell, and could have done so to let the Death Eaters in. Indeed, he could have relaxed it so that He and Harry would have had to go to Hogsmeade before going to the cave.)
Was this necklace a horcrux?
"Still very unwell, although she was relatively lucky. She appears to have brushed the necklace with the smallest possible amount of skin; there was a tiny hole in her glove. Had she put it on, had she even held it in her ungloved hand, she would have died, perhaps instantly. Luckily Professor Snape was able to do enough to prevent a rapid spread of the curse."Harry's question is a good one, and the close reader will see that it was sent to Snape rather than Madam Pomfrey because she would realize that the nedcklace was not really cursed, and did not cause Katie Bell's mishap.
"Why him?" asked Harry quickly. "Why not Madam Pomfrey?"
"Impertinent," said a soft voice from one of the portraits on the wall, and Phineas Nigellus Black, Sirius's great-great-grandfather, raised his head from his arms where he had appeared to be sleeping. "I would not have permitted a student to question the way Hogwarts operated in my day."
"Yes, thank you, Phineas," said Dumbledore quellingly. "Professor Snape knows much more about the Dark Arts than Madam Pomfrey, Harry. Anyway, the St. Mungo's staff are sending me hourly reports, and I am hopeful that Katie will make a full recovery in time."
C. The Invisibility Cloak
"Dumbledore" insists Harry bring along his invisibility cloak, at the end of chapter 3:
"We do not want to be encumbered by these just now," he said, pulling out his wand again. "I shall send them to the Burrow to await us there. However, I would like you to bring your Invisibility Cloak... just in case."This makes sense if "Dumbledore" wants Harry to have the cloak for Dumbledore's death scene, well planned in advance. But that is not what really happens. Rather, Dumbledore knows that all items brought into Hogwarts are scanned by Filch, or by Aurors, and he wants to switch Harry's Invisibility cloak for another one. This will just not do if Harry does not have the cloak on him. And so, Dumbledore's insistence.
Harry extracted his cloak from his trunk with some difficulty, trying not to show Dumbledore the mess within. When he had stuffed it into an inside pocket of his jacket, Dumbiedore waved his wand and the trunk, cage, and Hedwig vanished. Dumbledore then waved his wand again, and the front door opened onto cool, misty darkness.
Harry has the cloak with him on the train. Draco confronts him, freezes him in place (sound familiar?) and leaves him stranded there. Suddenly, Tonks appears. But Tonks is not Tonks. Snape recognizes that her Patronus is not Tonks' usual one - weaker than usual:
"Hagrid was late for the start-of-term feast, just like Potter here, so I took it instead. And incidentally," said Snape, standing back to allow Harry to pass him, "I was interested to see your new Patronus."Why mention the fleeting shock and anger, and why is is important that Harry (and thus the reader) fleetingly see it? This is unlike Tonks. It is not Tonks' Patronus because she is literally not herself.
He shut the gates in her face with a loud clang and tapped the chains with his wand again, so that they slithered, clinking, back into place.
"I think you were better off with the old one," said Snape, the malice in his voice unmistakable. "The new one looks weak."
As Snape swung the lantern about, Harry saw, fleetingly, a look of shock and anger on Tonks's face. Then she was covered in darkness once more.
Tonks knows exactly where to find Harry. How?
"How did you find me?"So she knew exactly what compartment to go to. I believe it was not because the blinds were drawn, but because Draco had told her, or because she is Draco (see comparison made between the two above, that both look thinner, and that she appears outside the room of requirement just as Harry is waiting outside to see what Draco is up to, after Harry had scared away Draco's two goons, which leaves only Draco.)
"I noticed you hadn't left the train and I knew you had that cloak. I thought you might be hiding for some reason. When I saw the blinds were drawn down on that compartment I thought I'd check."
When is the switch made? When Tonks finds him.
The train lurched, causing Harry to roll over onto his side. Now he was staring at the dusty underside of the seats instead of the ceiling. The floor began to vibrate as the engine roared into life. The Express was leaving and nobody knew he was still on it...She of course gives it back to him later:
Then he felt his Invisibility Cloak fly off him and a voice overhead said, "Wotcher, Harry."
There was a flash of red light and Harry's body unfroze; he was able to push himself into a more dignified sitting position, hastily wipe the blood off his bruised race with the back of his hand, and raise his head to look up at Tonks, who was holding the Invisibiliiy Cloak she had just pulled away.
"You'd better put that cloak back on, and we can walk up to the school," said Tonks, still unsmiling. As Harry swung the cloak back over himself, she waved her wand; an immense silvery four-legged creature erupted from it and streaked off into the darkness.Now, she also heals his nose:
"Episkey" said Tonks.But does not clean the blood off of his nose:
Harry's nose felt very hot, and then very cold. He raised a hand and felt gingerly. It seemed to be mended.
"Thanks a lot!"
"Where've you ... blimey, what've you done to your face?" said Ron, goggling at him along with everyone else in the vicinity. IThough it is strange Snape did not notice or comment. Why did she leave him looking awful? This is something Draco might wish to do.
"Why, what's wrong with it?" said Harry, grabbing a spoon and squinting at his distorted reflection.
"You're covered in blood!" said Hermione. "Come here ..."
She raised her wand, said "Tergeo!" and siphoned off the dried blood.
"Thanks," said Harry, feeling his now clean face. "How's my nose looking?
Finally, Rowling tells us straight out that Harry has unwittingly smuggled something into Hogwarts:
"Yeah, mine!" said Harry. "I told him at Kings Cross about Malfoy and that thing he was trying to get Borgin to fix! Well, if it's not at their house, he must have brought whatever it is to Hogwarts with him!"This is brilliant misdirection (Malfoy could not have smuggled anything in) while at the same time giving us the strong hint that Harry had not been searched.
"But how can he have done, Harry?" said Hermione, putting down the newspaper with a surprised look. "We were all searched when we arrived, weren't we?"
"Were you?" said Harry, taken aback. "I wasn't!"
"Oh no, of course you weren't, I forgot you were late. Well, Filch ran over all of us with Secrecy Sensors when we got into the entrance hall. Any Dark object would have been found, I know for a fact Crabbe had a shrunken head confiscated. So you see, Malfoy can't have brought in anything dangerous!"
Momentarily stymied, Harry watched Ginny Weasley playing with Arnold the Pygmy Puff for a while before seeing a way around this objection.
The alternate cloak (a horcrux?) could be switched any time later for Harry's real one.
The last two points are admittedly speculative:
D. The Wine
We know that the wine that accidentally poisoned Ron was sent to Slughorn. Purportedly this was so that it would somehow get to Dumbledore. How it would is not specified. I suspect that Slughorn was likely the intended recipient, to prevent Harry from finding the contents of Slughorn's memory about Horcruxes.
E. The Potion Book and the Half-Blood Prince?
Who is the more likely half-blood prince? Sure, Snape is half blood and his mother's name is Prince. But what about Voldemort? We are meant to suspect him throughout.
After all, Voldemort is a "prince" because he is of the Gaunt family. He is half-blood because of his father, Tom Riddle. He is likely to have used a borrowed version of the book, being poor, such that the book would have been kept as a backup by the school. (On the other hand, perhaps Snape, the previous teacher of the course, would have kept his own book from schoolhood days.) Voldemort is the more likely to half crossed out complicated potions and scornfully write "Just shove a bezoar down their throats." He is the type to, in childhood, construct spells to deal with "enemies," of the type that are quite potent and evil.
That Snape wanted the book so much could be attributed to his knowledge that this childhood book of Voldemort was in truth a horcrux. We see another book of Voldemort (the diary) was a horcrux. Harry hides the potion book in the room of requirement, intending to go back for it, but never does, and intends to not return to Hogwarts. The book is left in that room - I have a feeling we will see it in the next book.
Snape claims that he is the half-blood prince. Is this true, more misdirection, or a hint? Or is Snape really played by Voldemort?
All this is clearly much more speculative than the first two points.