The Lost Symbol

The Lost Symbol is a 2009 novel by the American writer Dan Brown. It is a thriller set in Washington DC after the events of The Da Vinci Code, and it relies on Freemasonry for both its recurring theme and its major characters.

The book was released on 15 September 2009, and it is the third of Brown's novels to feature the Harvard symbologist Robert Langdon, following Angels & Demons in 2000 and The Da Vinci Code in 2003. Each of the three follows the same pattern: a single compressed timeframe, a sequence of locations that can be visited, and a conspiracy assembled from symbols and historical material. This, the third Langdon novel, appeared in 2009, six years after The Da Vinci Code.

The material is presented as information as much as plot, and the settings are real buildings and institutions, which is the reason the books are read both as thrillers and as visitor's itineraries for the cities they use. The Freemasons are treated as a working society rather than as a secret, and their symbols, buildings and history supply both the clues and the people Langdon has to reason with.