Frank and Joe join Andrew Driscoll, the son of a professor, on a critical cross-country train ride. They are acting as decoys in a top-secret plan to transport a deadly virus from San Francisco to Chicago. In the wrong hands, the virus could unleash a biological catastrophe of unimaginable proportions!

But the plan goes haywire when Andrew disappears and the shocking truth about the Hardys' mission becomes clear. The boys begin to suspect that they are the ones ticketed for disaster, and that the end of the line -- for both them and the virus -- is dangerously near!