July 1878, and the West is teeming with astronomers eager to observe a total solar eclipse. Cora and four other female astronomy students have accompanied Professor Maria Mitchell to Colorado for the event, but their chances of seeing it are threatened when a railway dispute forces them to entrust their precious telescopes to a young freight hauler's wagon. Nolan Carter is determined to get his cargo and passengers to their destination, but as one thing after another goes wrong, he despairs of reaching Denver in time. Yet he could happily spend more time with the surprising Cora, who accompanies the telescopes while her companions take the train. Meanwhile, overhead, the celestial clock-indifferent to worldly dangers, delays, or distractions-is ticking.