''The Lost Symbol'', provisionally known as ''The Solomon Key'', is the third entry in DanBrown's novel series starring [[BadassBookworm Harvard symbologist Robert Langdon]]. This time, the story explores the mysteries of the Freemasons and is set in Washington D.C.. Langdon is invited to D.C. by an [[BigBrotherMentor old friend and mentor]] (and also not-so-secretly a top-rung Mason), only to discover that he has been an UnwittingPawn, manipulated by what seems to be a raving lunatic who kidnapped said mentor and now blackmails Langdon into solving the Freemasons' puzzles for him. The final prize in the game is the fabled treasure of [[MacGuffin Ancient Mysteries]], which, Langdon insists, is immaterial but he doesn't have much choice. As if that wasn't complicated enough, the [[CloakAndDagger CIA]] shows up and demands the very same things of Langdon... except that they couldn't care less about his mentor's safety.

A movie has been announced, but is in very early stages of production.
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!!The novel contains examples of:

* AdventurerArchaeologist: Langdon.
* AGodAmI: Mal'akh believes this fervently.
* AnOfferYouCantRefuse: Mal'akh needs Langdon's skills so he takes Peter hostage.
* AncientConspiracy: The book, and by extension Langdon, go through great lengths to disprove many common misconceptions and conspiracies about Freemasons.
* AncientTradition: The Freemasons. [[spoiler:And no, there is no AncientConspiracy here, neither imaginary nor real.]]
* ArbitrarySkepticism: Considering his previous two adventures, Langdon is really the last person in the world who should find it hard to believe that an ancient society is protecting a dangerous and powerful secret with hidden codes.
* AscendToAHigherPlaneOfExistence: The BigBad's master plan is to [[spoiler: sacrifice his body so he can ascend and lead the Forces of Evil in destroying mankind]]. Since Dan Brown's previous novels have generally taken place in "the real world" (ancient conspiracies and shoddy historical accuracy aside), you'd normally wouldn't count on it, except this novel throws in all that stuff about mental energies and the Noosphere being real.
* AsYouKnow: Practically Langdon's catchphrase.
* BadassBookworm: Langdon. Lampshaded when a security guard takes one look at Langdon and wonders how he managed elude the French police in ''loafers''.
* TheBeautifulElite: {{Deconstructed}}. While Katherine is good-looking and leads a highly privileged life, she has to face several tragedies, including the death of her father in her childhood, the [[spoiler: murder]] of her mother during Christmas time, and the ordeal involving her brother, Peter, that is the subject of this story.
* BrotherSisterTeam: Peter and Katherine, in a way.
* CallingTheOldManOut: [[spoiler: Zachary does this to Peter when he reveals his true identity.]]
* CIAEvilFBIGood: Except that FBI never shows up at all. [[spoiler:And CIA is revealed to be not ''that'' bad themselves.]]
* ContinuityNod: There are several references to Langdon's past adventures in the previous books.
* {{Claustrophobia}}: Langdon's fear of confined spaces is abused by the villain for an ingenious torture method.
* DanBrowned (of course): So, so much. Try the confusion between the meninges and the brain itself late in the book, for one.
* DeadpanSnarker: Most characters but Inoue Sato, Robert Langdon himself, Katherine Solomon and Mal'akh particularly qualify.
* DepravedBisexual - While depraved asexual at the time of the story, a throwaway line mentions that Mal'akh used to occasionally enjoy the company of young men in addition to women. Pretty much a classic example of this trope as making Mal'akh bi doesn't serve any purpose other than to making him even "stranger".
* DisproportionateRetribution: [[spoiler:Zachary's CallingTheOldManOut moment at the end turns everything he's done to Peter into this; Zachary's horrendous decision-making shamed his family and he squandered most of his wealth until he landed in prison, but apparently he turned to all of this because a.) his father refused to bribe a warden to get him released early to teach Zachary the meaning of responsibility, a lesson he ''badly'' needed, b.) Zachary changed his mind about the short-sighted decision between wealth or wisdom he made as a young man, and c.) the fact that Peter did not recognize Zachary, after [[InsaneTrollLogic Zachary had taken steroids, shaved his head, gotten tattoos, etc, etc.]]]]
** [[spoiler: Zachary's first beef was his having to decide between A. a pot of money right there and then, and B. the wisdom of the ancients revealed several years down the road ''plus'' that pot of money complete with interest, which included his dad's Good Ole Boy Network Approval, in whatever he planned to do. Zach grudgingly admits he hadn't thought things through at the time.]]
* EurekaMoment: Quite a few.
* {{Flashback}}: There's at least one every other chapter.
* GentlemanAndAScholar: Peter Solomon.
* GenderNeutralWriting: Used to conceal the fact that [[spoiler:Sato is actually a ''woman'']].
* GirlOfTheNovel: Notably averted, as the lead female character, Katherine Solomon, is fifty (making her closer to Langdon's age unlike the previous books) and her relationship with Langdon is a long-standing friendship. [[HotScientist But she's still attractive]].
* IHaveYourWife: In this case, "I have your best friend/brother."
* IdiotBall: It's been passed around a few times.
* ItsASmallNetAfterAll: Averted. In order to find what she's looking for on the net, Katherine has to link together hijacks other peoples' search engines and has them work together through ''parallel processing''. After that, she still has to sort out the junk from the useful stuff.
* LampshadeHanging: When Langdon's editor finds out where he is, his reaction is along the lines of "Oh god, not AGAIN".
* LukeYouAreMyFather: It's revealed that the main antagonist is actually [[spoiler:Peter Solomon's son Zachary]].
* MacGuffin
* MadLibThrillerTitle
* MyGodWhatHaveIDone: Bellamy when he realizes what Sato ''really'' wants.
* NamesToRunAwayFromReallyFast: The BigBad has these. Namely, Mal'akh a corrupted form of the name Moloch. Also Dr. Abaddon [[spoiler: Who happens to be the bad guy's psychiatrist alter ego.]]
* OhCrap: [[spoiler: Mal'akh]]'s reaction once he crosses over.
* OnlyAFleshWound: [[spoiler: After being rescued from imprisonment and torture, including having his hand forcibly amputated, kidnap victim Peter Solomon]] does not go into shock or collapse from loss of blood but instead indulges in a bit of light sightseeing and the delivery of several pages' worth of exposition.
* RedHerring: That mysterious redacted document that Katherine finds turns out to be [[spoiler:a CIA forum discussion about the meaning of [[http://en.wikipedia.org/wiki/Kryptos Kryptos']]]] true meaning, which happened to contain the exact same keywords she was looking for.
* RememberTheNewGuy: The previous books mentioned not a word about Solomon. All of a sudden he shows up and everyone has to suppose he is Langdon's father-mentor.
* RuleOfSymbolism: Well, duh, it's a DanBrown novel. Let's start with Mal'akh, more commonly known as [[http://en.wikipedia.org/wiki/Moloch Moloch]]...
* SamusIsAGirl: Inoue Sato.
* SelfDeprecation: The last plot twist in ''Literature/DigitalFortress'' is reused, and Langdon notes that he read about it in a "mediocre thriller".
* TheSociopath: Mal'akh.
* StrawFeminist: A light version in the form a student who complains about the lack of women in the Freemasons.
* TakeOverTheWorld: After acquiring the Lost Symbol and [[AscendToAHigherPlaneOfExistence becoming]] [[AGodAmI a god]] [[GodOfEvil in Hell]], this is what Mal'akh intends to do.
* UnsettlingGenderReveal - Inverted; Langdon doesn't realize Sato is a woman until they meet face to face, and she demands that he stop calling her "sir."
* UsefulNotes/WashingtonDC
* WhatCliffhanger
* WorldOfSnark
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