"The Jefferson Key" is a historical thriller novel by Steve Berry, featuring the character Cotton Malone. The story revolves around a secret society and a hidden message linked to Thomas Jefferson, the third President of the United States. Malone uncovers a conspiracy involving a centuries-old code that could threaten national security. As Malone delves deeper, he encounters various adversaries and allies, including the Knights of the Golden Circle, a group with ties to American history. The novel combines elements of adventure, history, and suspense, making it an engaging read for fans of the genre.