Pack your bags for a historic trip to the nation's capital. When Uncle Daniel sends a special invitation, the entire Bobbsey family boards a train to visit Washington, D.C. Bert, Nan, Flossie, and Freddie are absolutely amazed by the grand city. They spend their days marveling at the towering Washington Monument, taking exciting tours of the White House, and even sitting in to watch a real debate inside the giant Senate building. While sightseeing among the famous museums and beautiful monuments, the siblings cross paths with a worried young girl named Evelyn. She has lost a precious antique locket that belonged to her mother, and she has no idea how to find it in such a massive city. The twins, always eager to help a friend in need, immediately offer to track it down. You will follow the children as they search through the busy streets of the capital, hunting for clever clues and piecing together the timeline of the missing jewelry. Packed with fascinating American history and an exciting puzzle to solve, this classic story offers a wonderful mix of education, family fun, and an unforgettable detective adventure.