Syme is one of Winston's friends, who works in the Research Department of the Ministry of Truth and specializes in Newspeak. Syme is portrayed as an intelligent philologist and is considered an expert in Newspeak. During his conversation with Winston in the canteen, Syme displays his impressive knowledge of Newspeak as he elaborates on the changes they made to complete the definitive Eleventh Edition. Despite Syme's orthodox disposition and loyalty to Big Brother, Winston realizes that he will eventually be vaporized by the Party. Winston reasons that Syme is too intelligent and speaks too freely to continue living.

After a while, Syme simply disappears from the Research Department, and Winston realizes that he has been vaporized. Syme is eliminated by the Party and becomes an "unperson," which means that he never existed. All records and historical documents related to Syme are destroyed, and his memory simply vanishes from existence. Later on, O'Brien speaks to Winston and refers to Syme, who is an "unperson," which reveals that he is a member of the Brotherhood. O'Brien proceeds to invite Winston to his apartment, and Winston brings Julia along to join the secret organization. O'Brien then gives Winston Emmanuel Goldstein's Book, which reveals all the Party's secrets and confirms Syme's information regarding the systematic elimination of words to control rebellious thoughts. O'Brien also reveals that Winston and Julia will eventually be vaporized by the Party and cease to exist like Syme.

After having a conversation in the canteen with Syme, Winston has a flash of insight in which he realizes Syme will be vaporized because he's too intelligent. Their canteen conversation had been about the Newspeak dictionary Syme was working on. Syme had waxed enthusiastic about reducing the number of words in the language to the fewest possible. Syme had grasped that reducing people's vocabulary to a bare minimum reduced people's capacity to have subversive thoughts, and he talked about this knowledge openly with another person. In other words, he grasped the big picture in a way that violated the rules of doublethink, in which he was both to know and simultaneously remain unaware of what he was doing. Syme ends up disappearing, almost certainly vaporized.  O'Brien, apparently aware that Winston has talked to Syme, uses a mention of this "friend" of Winston's (since Syme has been vaporized O'Brien can't use his name) to suggest to Winston that he, O'Brien, might be a conspirator against the regime. 

O'Brien reveals a secret when he gives Winston a copy of The Book, laying bare the logic of Oligarchic Collectivism. The Book confirms what Syme had said about dumbing down the language: The Book reveals the importance of crimestop, or stopping any subversive thought before it can even occur. Syme clearly did not practice crimestop and, like Winston after reading The Book, he knew too much to be allowed to continue unchecked. 

Syme was eliminated by the party because he was intelligent. The author says,

“One of these days, thought Winston with deep conviction, Syme will be vaporized. He is too intelligent, he sees too clearly and plainly. The party does not like such people. One day he will disappear…”

After a while, Syme went missing and Winston was sure that Syme had been vaporized because not only did he fail to show up at work, but his name was also missing in the chess committee list of which he was part. After O’Brien cunningly affirms the belief of Winston and Julia in the brotherhood and its founder, the two pledge their allegiance to the Brotherhood and state that they would go to any length to advance the course of the Brotherhood in fighting the Party, even commit murder and suicide. O’Brien, who was an inner party member, cautioned them that if the Thought Police found them out the Brotherhood would not intervene and they would have to face the inevitable consequence. In the end after their release from the Ministry of Love, Winston awaits the bullet that will extinguish him.

Syme was vaporized.  Therefore, he never existed. This was predicted by Winston in the canteen when they were discussing Newspeak and the 11th edition of the Newspeak dictionary.  At the beginning of chapter 5 in Book 2, it states simply that “Syme had vanished” (147).  There is no further information regarding the specifics of his vaporization.  This is important regarding O’Brien, because when he speaks to Winston in chapter 6, he refers to Syme when he says, “I was talking recently to a friend of yours who is certainly an expert” (157).  Winston assumes that he is referring to Syme, but since Syme is now an unperson, no party member should reference him because he never existed according to Big Brother and the Party.  So, Winston takes this as a hint from O’Brien that he is sympathetic to the underground movement called “the Brotherhood”, because no party member, much less an inner Iparty member, would ever refer to an unperson.  As a result of this brief meeting, Winston and Julia end up at O’Brien’s home where they learn the secrets about the Brotherhood and the Book.