Hundreds of years after the events in Against the Fall of Night, Alvin and Seranis are working to repopulate the Earth with original species resurrected from a library of ancient genetic information. Among these resurrected beings is Cley, a Cro-Magnon and sole survivor of her tribe. Cley joins forces with Alvin and a large, intelligent rodent named Seeker to eliminate the threat from the Mad Mind once and for all-and clear the way for life in the Solar System to thrive.