The book's story takes place over a period of 12 hours in Washington, D.C., with a focus on Freemasonry. Langdon is summoned to Washington to give a lecture, apparently by his mentor, a Mason named Peter Solomon. However instead of an audience for his lecture he finds the severed right hand of Peter Solomon. Langdon begins a rapid chase through the basement of the Capitol building, solving a series of cryptic clues. He joins forces with Solomon's sister, Noetic scientist Dr. Katherine Solomon, while matching wits with Mal'akh, a tattooed, self-castrated and brilliant villain who is in search of an ancient source of power. The climax takes place in a Masonic Lodge. Mal'akh believes he has the "lost symbol". His death minutes later has a description of his soul being received by devils. The final chapters reveal more about the "lost symbol", and the book ends with the word "Hope".
