The Hansens look forward to a long family trip each summer, usually an RV trip to explore the amazing sites in the US. This year's trip to Washington, DC, however, gives them more excitement than they bargained for. During a visit to Ford's Theater, the site of President Abraham Lincoln's assassination, siblings TJ and Hannah Hansen believe they witness someone steal something from the theater's museum. They try in vain to convince their parents and the park rangers of what they saw, but no one believes them. To discover the truth, they enlist the help of their two younger brothers and embark on a dangerous journey, which leads them through the back streets and alleys of our nation's capital and threatens their very lives.