Geronimo Stilton is granted a special interview with the great Sourishi, who lives in isolation and rarely gives interviews. To reach him, Geronimo and company must take the Rodent-Express, a steam engine that zigs and zags across perilous terrain and steep mountains. But, during the journey, Bugsy Wugsy mysteriously disappears! Can Geronimo crack the case before the end of the line? It won't be easy when all the passengers are now suspects.
