Without lights and in a driving rain, a bus is lumbering along the muddy Assam Road en route from Chunking to the Indian border. Passengers include a European of unknown nationality, a missionary a French officer, and a White Russian. There is also an ancient Chinese lady on an important diplomatic mission to Indian and her traveling companion. The trip is halted when Japanese planes bomb the road and hit a munitions truck and kill many Chinese soldiers. The Chinese commander puts the wounded soldiers on the bus and directs it to a nearby secret airport where the officer in charge is an American attached to the Chinese Air Force.