Set in the nineteenth century against the rugged backdrop of the British Columbia Rockies and the building of Canada's first transcontinental railway, teen siblings Kate and Robbie lead pack horses across treacherous mountain terrain to deliver supplies to workers building the transcontinental railroad. Along the way, they befriend Lee, a young Chinese laborer with his own secret reasons for working to build the railway. The adventure takes a dramatic turn when Kate must disguise herself as a boy to stay at the railroad camp. While maintaining this secret, the teens are drawn into a daring mission to steer a supply barge through the dangerous Hell's Gate rapids, a critical step in completing the railroad. This gripping tale of courage and survival is based on a true but little-known story from Canada's past.