Treasure hunter Benjamin Franklin Gates looks to discover the truth behind the assassination of Abraham Lincoln, by uncovering the mystery within the 18 pages missing from assassin John Wilkes Booth's diary.
Just after the end of the Civil War, John Wilkes Booth and another man enter a bar and
approach Thomas Gates (Ben Gates' great-great grandfather). They produce a diary containing an encrypted message, and entice Thomas, a well-known puzzle solver, to decode it. Thomas recognizes the message as using the Playfair cipher and begins to translate it. While he does so, Booth leaves for the theater to assassinate President Lincoln. Thomas Gates solves the puzzle, a clue to a treasure map, and realizes the men are still loyal to the Confederate cause and have a sinister motive for finding the treasure. The Confederate man pulls a gun on him, threatening to shoot him if he doesn't hand over the diary, however he is distracted from Gates by the chaos erupting in the bar over news of Lincoln's assassination. Thomas rips several pages from the diary and throws them in the fireplace. The second man shoots him and attempts to retrieve the pages, only succeeding in saving a small piece. The dying Gates gasps, "The war is over," but the man disagrees, stating that "the war has only just begun," and rushes from the bar. With his dying breath, Thomas Gates tells his young son Charles, "The debt that all men pay."
Years later, Benjamin Gates is telling his great-great grandfather's story at a conference on Civilian Heroes to great acclaim until black market dealer Mitch Wilkinson shows one of the eighteen missing pages of John Wilkes Booth's diary, with Thomas Gates' name on it, convincing everyone that Gates was the mastermind behind the Lincoln assassination. Ben Gates sets out to prove the innocence of his great-great grandfather.
Using spectral imaging, Ben discovers a cipher pointing to Édouard Laboulaye hidden on the back of the diary page. He travels to Paris, where he finds a cryptic clue engraved on the torch of the French Statue of Liberty, referring to the two Resolute desks. Ben heads to Buckingham Palace, seeking out the closer of the two desks. With the help of his friend Riley Poole and estranged girlfriend, Abigail Chase, he is able to sneak into the Queen's office to find an ancient wooden plank hidden in the desk. He is then pursued by Wilkinson, who, having broken into his father Patrick Gates' house, has cloned Patrick's cell phone in order to track Ben's whereabouts. Wilkinson eventually obtains the piece, but not before Ben manages to photograph the symbols carved into the plank.
At Gates' insistence, Patrick reluctantly asks his ex-wife Emily Appleton Gates for help in translating the mysterious glyphs. 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, which is located in the Oval Office. With the unknowing help of Abigail's new boyfriend, who works for the White House, Ben and Abigail coax their way into the office to see the desk, where Ben discovers that the second plank is missing. However, he does find a stamp bearing the seal of the Book of Secrets. According to Riley, the Book of Secrets contains documents collected by Presidents for Presidents' eyes only, covering such controversial subjects as the JFK assassination, Watergate, and Area 51.
To find the location of the book, Ben forces the President's birthday party to be held at Mount Vernon by creating a rumor of cult gatherings at the currently planned location and by booking all other approved locations. When Ben sneaks into the party, he convinces the President to follow him into a secret tunnel under the house where he confronts him about the book. The President tells him the location of the book in the Library of Congress and tells him to read page 47 as well as the information he needs. In the book, Ben finds a picture of the plank from the desk and a note saying that President Coolidge found it in 1924 and had the Mount Rushmore monument built to hide the treasure. They do flip through the pages covering other controversial subjects, but they don't have time and those facts aren't revealed.
At Mount Rushmore, Ben, Riley, Abigail, and Patrick meet Mitch (who has kidnapped Emily). Mitch provides a clue to the entrance of a cave containing the legendary native American city of gold, Cíbola. They manage to find the city, but rising flood waters force them to leave. In the last room before the exit, a mechanism requires one person to stay behind while the others could leave. Mitch forces everyone to let him go first, but rising water forces him to be the last person left. Ben tries to help him out, but Mitch can't come to Ben without the door closing. Mitch decides to sacrifice himself and allow the others to escape the flooding cavern, and Gates agrees to give him credit for finding the treasure. Gates clears his family's name with the discovery and is cleared of all charges when the President tells everyone that Ben "saved his life," although he did nothing of the sort. Ben also ensures Mitch receives joint credit for the find. The President then asks Ben about what he read on page 47 of the Book of Secrets; Ben replies, "It's life-altering".
Afterwards, the city of gold has several archaeologists retrieving its gold. Riley meets a young woman who is a fan of his book while Ben and Abigail restart their relationship. The film ends when Riley reclaims his car (tax free) as a reward for finding the treasure, however he accidentally crashes it into a car when it goes in reverse.
Studios: Walt Disney Pictures
