The case of the soldier's ghost

From the author of the best-selling Field Trip Mysteries series comes Museum Mysteries, a series featuring an exciting group of intrepid young friends. A ghost has been spotted lurking around Capitol City's American History Museum. It seems someone or something is unhappy with the museum's recent exhibit on the Vietnam War. Can Raining Sam, the son of the head of educational programs at the museum, and his friends figure out who's behind the haunting before someone gets hurt?