Graustark.

While traveling by train from Denver to Washington, DC, wealthy young Grenfall Lorry meets a beautiful young girl. When they are accidentally left behind in a mining town, they race through the mountains and finally catch it. They travel to Washington and have a great time, but they soon part. They meet again later in the small European country of Graustark, where Grenfall and his friend Harry rescue her from kidnappers, and they then discover that she is actually the country's Princess Yetiva. She is engaged to Prinze Lorenz of Asphan in order to pay off Graustark's enormous debt from the war, but Lorenz is murdered and Grenfall is framed for the crime. Complications ensue.