In 1865, John Wilkes Booth and Michael O'Laughlen, both members of the Knights of the Golden Circle, enter a tavern and approach Thomas Gates (Ben Gates' great-great-grandfather), a well-known puzzle solver, to decode a message written in Booth's diary. Thomas begins to translate the message. While he does so, Booth leaves to assassinate President Abraham Lincoln. Thomas solves the puzzle, a clue to a map to Cibola, the city of gold, but realizes the men are still loyal to the South and have a sinister motive for finding the treasure. He rips several pages from the diary and throws them in the fireplace. Thomas is shot, and the gunman attempts to retrieve the pages, but only obtains a page fragment.Over 140 years later, Ben Gates (Nicolas Cage) is telling his great-great-grandfather's story at a Civilian Heroes conference. Black market dealer Mitch Wilkinson (Ed Harris) displays one of the 18 missing pages of John Wilkes Booth's diary, with Thomas Gates' name on it, convincing everyone that Thomas was not only a conspirator, but the grand architect of the Lincoln assassination. Ben sets out to prove the innocence of his great-great-grandfather. He discovers a cipher pointing to Édouard Laboulaye hidden on the back of the diary page. He travels to Paris, where he finds a clue engraved on the torch of the scale model of the Statue of Liberty on the Île aux Cygnes, referring to the two Resolute desks. Ben then heads to London to look at the desk at Buckingham Palace with the help of his friend Riley Poole (Justin Bartha) and estranged girlfriend, Abigail Chase (Diane Kruger). Ben makes a scene by pretending to be drunk and starting a fake argument with Abigail, and they are both arrested. Thanks to Riley who had previously hacked into the security system, they escape the cell and reach the desk via service elevator. From the Queen's desk, Ben obtains an ancient wooden plank with ancient symbols carved into it.
Meanwhile, Wilkinson clones Patrick Gates' (Jon Voight) cell phone in order to track Ben's whereabouts. Wilkinson eventually obtains the plank, but not before Ben manages to photograph it. At Ben's insistence, Patrick reluctantly asks his ex-wife and Ben's mother, Dr. Emily Appleton (Helen Mirren) for help in translating the symbols. She does so, but points out that some of the glyphs are partial, leading Ben to conclude another plank must be hidden in the other Resolute desk in the Oval Office. Ben and Abigail coax Abigail's new love interest, Connor (Ty Burrell), who works at the White House, into letting them into the office to see the desk. Ben discovers that the second plank is missing, but he does find a stamp bearing the seal of the Book of Secrets. Riley tells Ben that the Book of Secrets contains documents collected by presidents for presidents' eyes only, covering such controversial subjects as the eighteen minutes erased from the Watergate tapes, Area 51, and the assassination of John F. Kennedy.
Ben crashes the President's birthday party at Mount Vernon. He convinces the President (Bruce Greenwood) to follow him into a secret tunnel where he confronts him about the book; the President sympathetically warns Ben that his actions will be interpreted as an attempt to kidnap the president, which is a federal offense. The President reveals the location of the book, in the Library of Congress.
In the book, Ben finds a picture of the missing plank from the desk and an entry by President Coolidge, who found the plank in 1924, had it destroyed, and commissioned Gutzon Borglum to carve Mount Rushmore to erase the map's landmarks. Ben, Riley, Abigail, and Patrick head to Mount Rushmore where they meet Wilkinson, who has kidnapped Ben's mother. He helps them find the entrance of a cave containing the legendary Native American city of gold, Cíbola. After encountering several traps, they eventually find the city of gold behind Mount Rushmore. However, in order to leave the city of gold when it suddenly begins flooding, one person has to stay behind to hold open the stone door to the drainage tunnel beneath the city, an action which would result in certain death. When Ben becomes trapped under the door, Wilkinson has to choose either to stay behind and sacrifice himself or everybody will drown. He chooses to give the others a chance to escape, and Ben promises to give Wilkinson part of the credit for discovering himself.
Ben clears his family's name with the discovery and is cleared of all charges when the President tells everyone that Ben did not kidnap him, but actually saved his life when the secret passage they were looking at was accidentally activated. Everyone including Wilkinson is given credit for the discovery of the Lost City of Gold.
- Nicolas Cage as Benjamin Gates
- Jon Voight as Patrick Gates, Ben's father
- Harvey Keitel as Peter Sadusky
- Alicia Coppola as Special Agent Spellman
- Ed Harris as Mitch Wilkinson, a black market dealer
- Diane Kruger as Dr. Abigail Chase, Ben's colleague and girlfriend
- Justin Bartha as Riley Poole, Ben's colleague
- Bruce Greenwood as President of the United States
- Helen Mirren as Dr. Emily Appleton, Ben's mother
- Joel Gretsch as Thomas Gates
- Billy Unger as Charles Gates
- Ty Burrell as Connor, Abigail's new boyfriend
- Zachary Gordon as Lincoln Conspiracy Kid
National Treasure 2: Book of Secrets received generally negative reviews from critics. Rotten Tomatoes reported that 32% of critics gave the film positive reviews based on 101 reviews. Metacritic reported the film had an average score of 48 out of 100, based on 25 reviews, while British film critics disputed the implication of British support for the Confederate side in the American Civil War. It opened at number one with $16,739,339 on its first day, and $44,783,772 its first weekend, the third largest Christmas opening. It reached the $100 million mark in eight days, half the time it took the first film. It stayed at number one for 17 days before dropping to number two, and grossed $457,364,600 worldwide, making it the ninth highest grossing film of 2007.
Disney Press published an official novelization of the screenplay titled National Treasure 2: Book of Secrets The Junior Novel on November 6, 2007. Parts of the story in the novel version differ slightly from what was actually filmed, owing to changes being made in the screenplay prior to and during production. For example, in the novel, Ben and Abigail photograph the wooden plank found hidden in the Queen's desk and leave it behind, with the car chase following. But in the movie, they take the plank with them on the chase.
Also published on the same day as the official novelization was a companion youth novel Changing Tides: A Gates Family Mystery by Catherine Hapka. Its story is set in England in the year 1612 and is the first in a series of planned historical novels about the Gates family. The epilogue from Changing Tides is included at the back of the National Treasure book. The second youth novel by Hapka, Midnight Ride: A Gates Family Mystery, was published on March 8, 2008.
National Treasure: Book of Secrets was released on DVD, UMD, and Blu-ray Disc on May 20, 2008 (June 2, 2008 in the UK). In the opening weekend, 3,178,631 DVD units were sold, bringing in $50,826,310 in revenue. As of August 2009, 5,873,640 DVD units have been sold, generating revenue of $93,132,076. This does not include Blu-ray Disc sales or DVD rentals.
The film has been retitled National Treasure 2: Book of Secrets for all three releases. The film's official website has also been changed accordingly.
Many scenes of historic locations were filmed on location, including the scenes at Mount Vernon and Mount Rushmore.  Filming at Mount Rushmore took longer than initially scheduled, due to inclement weather and the decision to changing the setting of additional scenes to the area around Mount Rushmore to take advantage of Black Hills backdrop.
Director Jon Turteltaub said that the film-making team will take its time on a second National Treasure sequel, but Disney has already registered the domains for NationalTreasure3DVD.com and NationalTreasure4DVD.com. Though the second film ended with the question about page 47 of the President's book of secrets, Turteltaub responded in a press interview that the idea was not set in stone as the basis for National Treasure 3. The Internet Movie Database slates the third film for release in 2014 with the original cast consisting of Nicolas Cage, Diane Kruger, Justin Bartha, Jon Voight, and Helen Mirren returning again.