Something's brewing at the National Portrait Gallery Museum in Washington, D.C. twelve-year-old Art is sure of it. But his only proof that a grand heist is about to take place is iced mocha, forty-two steps, and a mysterious woman who appears like clockwork in the museum.

When Art convinces his best friend, Camille, that the heist is real, the two begin a thrilling chase through D.C. to uncover a villainous scheme that could be the biggest heist since the Isabelle Stewart Gardner Museum theft in 1990. With a billion dollars' worth of paintings on the line, the clock is ticking for Art and Camille to solve the conspiracy.