Why could Harry open the door to the The Department of Mysteries when Snape invaded his mind?

Question

In the Order of the Phoenix, Harry was always dreaming about a mysterious door. He had seen the door before but never had the chance to go inside. However, when Snape used Legilimency on Harry in one of their lessons, Harry was forced to see the door open, which he'd never dreamed about:

He was hurtling along the corridor towards the Department of Mysteries, past the blank stone walls, past the torches – the plain black door was growing ever larger; he was moving so fast he was going to collide with it, he was feet from it and again he could see that chink of faint blue light –

The door had flown open! He was through it at last, inside a black-walled, black-floored circular room lit with blue-flamed candles, and there were more doors all around him – he needed to go on – but which door ought he to take –?

‘POTTER!’

Harry opened his eyes. He was flat on his back again with no memory of having got there; he was also panting as though he really had run the length of the Department of Mysteries corridor, really had sprinted through the black door and found the circular room.

‘Explain yourself!’ said Snape, who was standing over him, looking furious.

‘I ... dunno what happened,’ said Harry truthfully, standing up. There was a lump on the back of his head from where he had hit the ground and he felt feverish. ‘I’ve never seen that before. I mean, I told you, I’ve dreamed about the door ... but it’s never opened before ...’ (Harry Potter and the Order of the Phoenix, UK edition, pp.522-523)

Does this suggest Harry was looking through Nagini's eyes because of the Horcrux connection between them? Nagini might be lurking around the Department of Mysteries and manage to get inside, but I haven't found any canon to support that yet.

So is it possible that at that point Voldemort was planting fake memories in Harry's mind? Maybe neither Voldemort nor Nagini had been inside the circular room in the DoM and he might just imagine the whole scene up according to what Rookwood had described to him.

Which theory is more plausible? Or is there a third explanation?

Answer 1

Because Voldemort knew what was inside

First, we must recognize that (aside from the final vision, that of Voldemort torturing Sirius) the dreams that Harry had were not planted by Voldemort. They were simply a natural consequence of the bond between Harry and Voldemort.

“Professor Snape discovered,” Dumbledore resumed, “that you had been dreaming about the door to the Department of Mysteries for months. Voldemort, of course, had been obsessed with the possibility of hearing the prophecy ever since he regained his body, and as he dwelled on the door, so did you, though you did not know what it meant.

—Harry Potter and the Order of the Phoenix

Since Voldemort was constantly thinking about the door, Harry saw it in his dreams.

Further, Snape purposely tried to hurt Harry during his Occlumency lessons, due to his dislike for Harry. As Harry noted, this actually increased his vulnerability to Voldemort's influence (conscious or unconscious):

“Snape made it worse, my scar always hurt worse after lessons with him —” Harry remembered Ron’s thoughts on the subject and plunged on. “How do you know he wasn’t trying to soften me up for Voldemort, make it easier for him to get inside my —”

“I trust Severus Snape,” said Dumbledore simply. “But I forgot — another old man’s mistake — that some wounds run too deep for the healing. I thought Professor Snape could overcome his feelings about your father — I was wrong.”

—Harry Potter and the Order of the Phoenix

In other words, during his Occlumency lessons Harry was more receptive to Voldemort's thoughts.

The scene in question took place right after Harry had used a Shield Charm to reverse Snape's Legilimency on him. As such, Harry believed that Snape was going to punish him for his actions (presumably by invading his mind painfully).

Harry felt a thrill of dread: He was about to pay for what had just happened, he was sure of it. They moved back into position with the desk between them, Harry feeling he was going to find it much harder to empty his mind this time....

—Harry Potter and the Order of the Phoenix

Snape was loyal to Dumbledore, but he hated Harry. He enjoyed making Harry look inadequate, to the point where he would tear down Harry's mental defenses out of sadism. He had probably just done this before Harry had his vision of the Department of Mysteries. This allowed Voldemort's thoughts to come through more easily. As such, this new vision was not a memory, but a picture of what Voldemort was thinking about at that moment.

---

How did Voldemort know what was in the Department of Mysteries?

• He might have been there for some reason when he was younger.
• More likely, he had acquired the information directly from the mind of Rookwood, who had been an unspeakable and had presumably been at least in the antechamber.

Answer 2

Harry has had be asleep whenever Voldemort tried to plant the vision of the Department of Mysteries inside Harry's mind, Harry had never even seen nor heard of that place before. So the fact that he could see that corridor and what was inside it has got nothing to do with Harry. He could always open that door and see what was inside, as he was always seeing what Voldemort wanted to plant in his mind, but whenever Voldemort was about to show him what was inside the door in the previous occasions, he had always woke up, breaking the connection between his mind and Voldemort's. During the legilimency attacks however, his mind seemed to be more vulnerable to the visions from Voldemort and the connection was there long enough for Voldemort to be able to just show what was inside the door. Harry would probably have seem more, had it not been for Professor Snape breaking the connection.

During the battle at the Ministry it is hinted that Voldemort never really was there when Harry saw him torturing Sirius. This seems to indicate that he doesn't really need to be there in order to plant visions of that place in Harry's mind. The only time he was really there was during the attack on Arthur Weasly. He could probably plant any images he wished whenever Harry wasn't completely conscious.

Answer 3

While it is true (as a previous answer has pointed out) that sometimes Harry was startled awake before he would have had a chance to open the door, that appears to have just been coincidental. He had the dreams almost every night and until that session with Snape he had never been able to open the door, even when he wasn't startled awake:

What was more, he was now dreaming about walking down the corridor toward the entrance to the Department of Mysteries almost every night, dreams that always culminated in him standing longingly in front of the plain black door.

I believe there is a simple explanation as to why he suddenly was able to open the door. First, though, we must note that he was able to open the door in subsequent dreams as well, for instance:

He had fallen right into the corridor leading to the Department of Mysteries. He was speeding toward the plain black door... Let it open... Let it open... It did. He was inside the circular room lined with doors... He crossed it, placed his hand upon an identical door, and it swung inward...

So it appears that there was a turning point in Harry's dreams. Up until the session with Snape he had been unable to open the door; from that session and on he was able to open the door.

So what changed?

The answer is, I believe, that Voldemort changed. The key passage here comes from the end of the book, when Lucius Malfoy explains about the prophecy (my emphasis):

“Dumbledore never told you?” Malfoy repeated. “Well, this explains why you didn’t come earlier, Potter, the Dark Lord wondered why —”

“— when I say go —”

“— you didn’t come running when he showed you the place where it was hidden in your dreams. He thought natural curiosity would make you want to hear the exact wording...”

I think Lucius was saying that Voldemort deliberately showed Harry the place in his dreams in order to get him to come retrieve it. However, this deliberate showing was a late development.

For the first half of the year Voldemort did not realize that he had a mind connection with Harry. As such, everything that Harry saw was unintentional from Voldemort's perspective; Harry was simply seeing what Voldemort's mind was preoccupied with.

This is explicitly stated by Snape during the first Occlumency lesson:

“It appears that the Dark Lord has been unaware of the connection between you and himself until very recently. Up till now it seems that you have been experiencing his emotions and sharing his thoughts without his being any the wiser. However, the vision you had shortly before Christmas —”

However, when Harry saw the attack on Mr. Weasley, he penetrated far enough into Voldemort's mind that Voldemort found out about the connection. This too is stated by Snape during the first Occlumency lesson:

“It is enough that we know,” said Snape repressively. “The important point is that the Dark Lord is now aware that you are gaining access to his thoughts and feelings. He has also deduced that the process is likely to work in reverse; that is to say, he has realized that he might be able to access your thoughts and feelings in return —”

It was only from this point on that Voldemort was able to use the connection to manipulate Harry, because it was only from this point on that he knew about the connection.

Now Voldemort obviously knew what the Department of Mysteries looked like, or else Harry would never have been able to get past the door. However, during the time before Voldemort realized there was a connection, the door never opened because that is what Voldemort's mind was occupied with. I.e. he was trying to find a way to get into the Department of Mysteries. What lay beyond the door was irrelevant to his thoughts at the time. All that mattered was getting through the door.

When he realized there was a connection he was no closer to being able to get through the door. However, at that point he realized he could use Harry by playing to his curiosity. Merely seeing a corridor with a door at the end would hardly be enough too get Harry to do anything foolish, so Voldemort upped the ante. He began showing Harry what lay beyond the door, giving him very specific looks into the Department of Mysteries so that Harry would be able to figure out how to retrieve the prophecy, as in this dream:

Last night he had once again made the journey along the Department of Mysteries corridor. He had passed through the circular room, then the room full of clicking and dancing light, until he found himself again inside that cavernous room full of shelves on which were ranged dusty glass spheres...

He had hurried straight toward row number ninety-seven, turned left, and ran along it... It had probably been then that he had spoken aloud... Just a bit farther... for he could feel his conscious self struggling to wake... and before he had reached the end of the row, he had found himself lying in bed again, gazing up at the canopy of his four-poster.

It just happened to be that Voldemort's plan didn't work so well, as Lucius acknowledged, because Harry didn't know about the prophecy to begin with.

So in short, there was nothing special about the particular session with Snape that allowed Harry to open the door. It was simply that up to that point the door had never opened because Voldemort, not realizing that Harry was watching, didn't care what was beyond the door. It was only once he realized that Harry was watching that he began to deliberately show Harry what was beyond the door.

Answer 4

I theorise at this point, Voldemort had already started reverse planting the images into Harrys mind, and it wasn't Harry's own doing that allowed him to see the door open, but it was already planted there by Voldemort. Voldemort himself may have seen the door (or sent Nagini) at a different point beforehand to get the images.

Using Legilimency, Snape could see and drill into Harry's mind and flashes of things even Harry himself didn't remember he had from his past. So when Snape used "Legilimens" on Harry to penetrate his mind, and saw the door open, Snape must have known that Voldemort was able to plant images deep into Harrys mind (yet Harry was unaware of them still), which is exactly what the Order feared, and why Snape was so angry.

tldr; Voldemort planted door opening in Harrys mind at one point before the lesson, Snape found out via Legilimency, confirming Order suspicions that Voldemort could plant into Harrys mind.

Answer 5

A lot of good theories here, some right and some wrong. Here's what really is true.

Voldemort as we know had been plotting to retrieve the prophecy ever since his return. However, the revelation that prophecies can only be retrieved by those to whom they are about from the Department of Mysteries was not even known to Voldemort until around March of 1996 in the chapter "Seen & Unforeseen," when Voldemort finally gets to interrogate Rookwood and pull information from him. If you've done your homework you know that Rookwood was previously an unspeakable in the Department of Mysteries before his arrest which is shown in Dumbledore's memory of Ludo Bagman's trial in the Goblet of Fire.

Furthermore, prior to Nagini's attack on Arthur Weasley Voldemort had no idea that Harry was in his mind. As such, when Voldemort was obsessing and dwelling on retrieving the prophecy he had no intentions of having Harry Potter - his worst enemy - retrieve it.

Even after Nagini's attack Voldemort did not dwell on actually entering the Department of Mysteries simply because it was suspicious and dangerous to his secrecy, he was simply dwelling on the corridor leading to it, nor was his plan to draw Harry there. If we remember back on August 31, Voldemort was furious for Sturgis Podmore being arrested and not retrieving the prophecy, remember Sturgis, a member of the Order, was under Malfoy's Imperius curse at the time. If we fast forward again to around December of 1995, we know that Broderick Bode, an unspeakable, could not retrieve the prophecy under Malfoy's Imperius curse and Avery, one of Voldemort's Death Eaters, had relayed false information to Voldemort on accident not knowing why Bode failed in retrieving the prophecy. Avery was severely punished for this. We know it's because the prophecy was not made out to Bode. At this point Voldemort needs an inside worker. Bode is useless now and mad in St. Mungo's and The Dark Lord has his servants dispose of him. But The Dark Lord has another trick up his sleeve. He has been planning the breakout from Azkaban of his top lieutenants meticulously since September of 1995 or even earlier. We know this because Harry has a flash of Voldemort's mood in Umbridge's detention the first week of school. Later Harry reveals that Voldemort was happy. Later in October we know Voldemort is really angry because Harry says after his vision after Quidditch practice that Voldemort wants something done and it's not happening quick enough. So Voldemort bides his time and scouts out the Department of Mysteries with Nagini until the Azkaban breakout.

After the breakout in January of 1996, it takes about a month to a month and a half before Voldemort is able to securely get his Death Eaters together and talk to Rookwood see Ch. 26 "Seen & Unforeseen." The Occlumency lesson with Snape you are specifically referring to happens just pages after the encounter with Rookwood. Rookwood supplies the Dark Lord with what he needs which is all the information he can give to The Dark Lord about the Department and the Hall of Prophecy. Therefore, Voldemort now knows more about the Hall of Prophecy and The Room of Doors and Voldemort is able to enter The Department of Mysteries in his mindscape probably from going through Rookwood's memories which is why the door in this Occlumency lesson opens. It is here that Voldemort now constantly thinks of it as he is closer to knowing where the prophecy is and how to get to it. He also decides to formulate a new plan to get the prophecy that involves Harry because he cannot enter the Ministry without exposing himself. Remember, Voldemort also thought Harry knew about the prophecy so Voldemort must have thought that he need not do anything besides dwell on the prophecy's exact location for Harry to go retrieve it for him. In Ch. 37 Dumbledore even acknowledges this

"And then you saw Rookwood (which Snape discovers from Harry's mind in a later Occlumency lesson) who worked in the Department of Mysteries before his arrest, telling Voldemort what we had known all along - that the prophecies held in the Ministry of Magic are heavily protected. Only the people to whom they refer can lift them from the shelves without suffering madness."

At this point now, Voldemort is both obsessing over finding the prophecy and attempting to lure Harry to the Department of Mysteries, which is his new formulated plan since March of 1996. Malfoy specifically says so in Ch. 35.

"Dumbledore never told you?'" Malfoy repeated. "Well this explains why you didn't come earlier Potter, the Dark Lord wondered why- you didn't come running when the Dark Lord showed you the place where it was hidden in your dreams."

As such, we now know that the door never swung open before because the information was not present for Voldemort to either know what exactly lay beyond the door, or lure his greatest enemy to it, until about March and that specific Occlumency lesson when Harry's mind was most vulnerable. Someone else earlier pointed out how Snape made Harry have more dreams about the corridor and the Department and that is true but as we now also know, not on purpose. This is because of Harry's inability to block out his hatred for Snape during Occlumency lessons. Again, this makes Harry more susceptible to these nightly strolls down the corridor.

After Rookwood tells him this is then when Voldemort switches up his plan to have Harry go retrieve the prophecy. He thought like stated earlier that natural curiosity would make Harry go to the Department because he is reckless. However, Harry never knew about a prophecy so he just was curious about "the weapon" that the The Order had mentioned earlier in August of 1995 to which Harry had unraveled was in The Department of Mysteries during his first Occlumecy lesson. It was there that he realized the corridor he had been dreaming about, the one with "the weapon" behind its door, he had seen on his way to his hearing on August the Twelfth in the Ministry of Magic.

It isn't until mid to late June that Voldemort has to switch his strategy up and plant a very clever vision into Harry's mind of Sirius being tortured.This is because Harry as a student, has no reason to go to London for a "weapon" that is unknown to him and one he thinks the Order most likely has under control from March through June. Voldemort as such, then has to manipulate Harry and create that false vision of Sirius. In addition, all other dreams and visions besides the one about Sirius were either happening in real time or it was Voldemort thinking and contemplating entering the Department of Mysteries and the Hall of Prophecy which were most likely Voldemort's retrieved memories from Rookwood's time as an unspeakable and spot on accurate portrayals of the landscape of the Department of Mysteries, which is why Harry knows exactly where to go when they get to the Ministry of Magic.

So there you go. It's an interesting mystery that took a lot of research but of course those are the best kind. I think this mystery was answered satisfactorily by the book but there is still many aspects to it that many readers don't recognize until a reread, but considering how long it is I can't blame Jo. If you go back you can see evidence in all of Harry's dreams and it is quite plain then. Dumbledore focuses a little bit on it at the end but not as much to answer the question fully. But still, the book was so long that the reader has to answer many questions for themselves, so I hoped this helped!