After arriving in Denver, Colorado, Tex, Carson and Kit set out to investigate mysterious secret jobs that are sabotaging the construction of the railroad. Mine owner James Horton also becomes a victim of criminal thuggery. In the whirlwind of adventure, our heroes, appearing under false names, solve the riddle of the missing Mrs. Horton. After the situation is resolved, Tex and both Kits head to Kansas, but on the way they encounter a village half destroyed by fire. The crime seems to be the work of the Pawnee Indians, but during the investigations, the rangers find out that it is also a kola that holds the entire territory of North Carolina in its grip.