The Lost Symbol by Dan Brown‎

Famed Harvard symbologist Robert Langdon answers an unexpected summons to deliver a lecture at the U.S. Capitol Building. His plans are interrupted when a disturbing object—artfully encoded with five symbols—is discovered in the building. Langdon recognizes in the find an ancient invitation into a lost world of esoteric, potentially dangerous wisdom.  When his mentor, Peter Solomon—a long-standing Mason and beloved philanthropist—is kidnapped, Langdon realizes that the only way to save Solomon is to accept the mystical invitation and plunge headlong into a clandestine world of Masonic secrets, hidden history, and one inconceivable truth . . . all under the watchful eye of a terrifying enemy.