Warren Spalding and Betsy Tyler have been assigned to do a paper on the Johnstown Flood of May 31, 1889. This time they've decided no to use the Instant Commuter time-travel device. It's too dangerous. After all, they nearly died on two previous assignments.
So they interview ninety-five-year-old Doc Keaton, whose parents survived the flood. But when they learn that Doc still mourns his little sister who died, Warren and Betsy secretly agree to travel back to 1889, to find eight-year-old Anna and save any lives they can.