I read something online that got me thinking about this. Why didn't Voldemort suspect Snape had defected from the Death Eaters and was now working for Dumbledore during the events of *Philosopher's Stone?

Voldemort was possessing Quirrell's body and his head was protruding from the back of Quirrell's - in other words, Voldemort was with Quirrell constantly during the events of Philosopher's Stone, presumably overhearing whatever Quirrell himself heard.

Snape cornered Quirrell more than once (Halloween, when Quirrell let the troll in, and the night Harry broke into the Restricted Section over the Christmas holidays to look for information on Nicholas Flamel) and openly threatened him against working for Voldemort and pressuring him to declare his loyalties to Dumbledore. This obviously revealed Snape's loyalty to Dumbledore to Quirrell, and presumably Voldemort, and I can't think of a reason why Voldemort wouldn't have been able to hear Snape strong-arming Quirrell perfectly clearly.

Why didn't Voldemort attempt to make contact with Snape during Philosopher's Stone? After all, Snape was supposedly Voldemort's most faithful servant. How is it Voldemort didn't suspect Snape was working for Dumbledore and didn't orchestrate a move against him? Snape wasn't even pretending to be a double agent during Philosopher's Stone, so why Voldemort didn't kill Snape as soon as he was physically able, or have Quirrell attempt to kill him, is unclear.

So yes, why didn't Voldemort suspect Snape as a double agent during the events of Philosopher's Stone?

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    Perhaps Voldemort's arrogance blinded him from the possibility that Snape was a double-agent aligned to someone other than himself. The tricky thing about a double-agent is where their true allegiance lies. Commented Jun 21, 2012 at 2:25
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    Because he's a schmuck.
    – Valorum
    Commented May 22, 2015 at 19:00
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    I think the Dark Lord and Professor Dumbledore both knew that Professor Snape was a double agent. He was leaking information to both of them. The difficult question is just whether he'd be ultimately loyal to one of them in the end.
    – b_jonas
    Commented May 22, 2015 at 21:21
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    Was Snape ever supposed to have been Voldemort’s “most loyal servant”? When is that ever stated? Remember the graveyard: “And here we have six missing Death Eaters ... three dead in my service. One, too cowardly to return ... he will pay. One, who I believe has left me forever ... he will be killed, of course ...”. The last one is clearly Snape—Voldemort thought, quite understandably, that Snape was working for Dumbledore and had left the Death Eater ranks. As to why he didn't kill him through Quirrell—why risk it? He was after the Stone and life; revenge can always come later. Commented Jan 30, 2016 at 17:20
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    Are you sure the "One, who has left me forever..." referred to Snape? In the light of HBP, I would have thought Voldemort was referring to Regulus Black.
    – Wallnut
    Commented Nov 12, 2018 at 17:17

5 Answers 5


From The Half Blood Prince:(emphasis mine)

“I think you next wanted to know,” he pressed on, a little more loudly, for Bellatrix showed every sign of interrupting, “why I stood between the Dark Lord and the Sorcerer’s Stone. That is easily answered. He did not know whether he could trust me. He thought, like you, that I had turned from faithful Death Eater to Dumbledore’s stooge. He was in a pitiable condition, very weak, sharing the body of a mediocre wizard. He did not dare reveal himself to a former ally if that ally might turn him over to Dumbledore or the Ministry. I deeply regret that he did not trust me. He would have returned to power three years sooner. As it was, I saw only greedy and unworthy Quirrell attempting to steal the stone and, I admit, I did all I could to thwart him.”

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    Oh, good catch in Half-Blood Prince. Perfect! :) Commented Oct 7, 2012 at 17:12

I think it's worth answering here because the question references Voldemort's thinking during the events of Philosopher's Stone - none of the answers I see truly address the situation from that perspective so here goes:

Looking solely at the text of Book 1 - there would be no reason for Voldemort to think Snape had necessarily turned against him. Consider the scene between Snape and Quirrell in the forest:

"Oh I thought we'd keep this private", said Snape, his voice icy. "Students aren't supposed to know about the Sorcerer's Stone, after all"

Later in the exchange, he says:

"Have you found out how to get past that beast of Hagrid's yet?"

Then finally:

"You don't want me as your enemy Quirrell."

Consider this interaction from Voldemort's point of view:

Snape doesn't know Quirrell is evil, so, he (Vold) assumes that Snape considers Quirrell as legitimate and working for Dumbledore, protecting the Stone. From Voldemort's point of view, if Snape likewise were working for Dumbledore and attempting to protect the stone, why would he be accosting somebody on the same team for information about how to purloin the stone?

From this perspective, Snape is clearly evil: in fact, this is what we are supposed to think, given that we see the interaction from Harry's point of view, Harry comes away resolute in his opinion that once and for all, Snape is disloyal and evil - exactly what Voldemort would think as well, which, to him, Voldemort, is a positive situation.

Quirrell later asserts to Harry that he believed Snape was onto him:

He suspected me all along. Tried to frighten me..."

Ultimately though, had Snape, from Voldemort's perspective, truly considered Quirrell an objective danger to Dumbledore's plans for the stone, Snape would have turned to Dumbledore. Instead, Snape seems to be pursuing this on his own, which logically means Snape isn't looking out for Dumbledore's plans, but his (Snape's) own plans.

Voldemort had no reason in Book 1 to distrust Snape because Snape, as always, never revealed his ultimate loyalty.


Maybe Voldemort assumed that Snape was pretending to be loyal to Dumbledore. After all, the dark lord hadn't revealed himself to Snape yet, and Voldemort, being the mastermind he was, knew that a double agent would have to keep up appearances. Perhaps Voldemort thought Snape was biding his time till the Dark Lord rose once again (while also protecting the stone from another professor whom Snape assumed was attempting to steal the stone). As long as Voldemort remained hidden, he knew it was best for Snape to appear loyal to Dumbledore in anyway possible.


Voldemort must have thought that Snape didn't know Voldemort was inside the body of Quirrell, He just had to keep the stone safe, because he wouldn't get trusted by dumbledore.

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    Given that this actually the truth, and that it was made before @NomSim s answer, why the downvotes? Commented Jul 8, 2015 at 14:35
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    @jokeSlayer94 This answer was posted almost three years after the accepted answer. The accepted answer also provides a relevant quote from the books, while this is short and sounds like unsupported speculation without supporting evidence. Commented Jan 30, 2016 at 20:43

Personally I think that Prof Quirrell didn't reveal to Snape that night when Snape confronted him in the hallway outside of the library in Sorceror's Stone, why he was actually looking for the stone. All we saw was that Snape was telling him not to make an enemy of Snape. Voldemort wouldn't want Quirrell to blow his cover thus loosing the element of surprise. And Voldemort would have expected Snape to keep up appearances while still being planted at Hogwarts. I've thought of this topic myself, very clever move by Rowling.

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    Hi, welcome to the SciFi&Fantasy Stack Exchange! Generally speaking, it is encouraged to make answers that are 'fact-based' rather than opinion-based. Thus, you should back up your answer with evidence from the books or from J.K. Rowling.
    – DBPriGuy
    Commented Oct 6, 2016 at 19:44

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