Hoping to escape the attention brought on by the accident that flattened Stanley, the Lambchop family drives to South Dakota, where they become involved in a wild west adventure at Mount Rushmore.

When a missing page from the diary of John Wilkes Booth surfaces, Ben Gates' great-great grandfather is suddenly implicated as a key conspirator in the assassination of Abraham Lincoln. The page is one of 18 pages missing from Booth's diary. When doing more research, the conspiracy takes Ben, Abigail, and Riley from Buckingham Palace to the White House - both places they break into - and even stealing a page from a secret book. But in order to see...