With this story we descend in our subconscious. The kind of subconsciousness that all men and women have, from the dawn of mankind till the present day. Sometimes in our dreams we are able to catch a glimpse of that subconscious: we fall down a steep slope. We use our hands and feet to slow down the fall and finally we reach the ground without injuries.
Tormented by a succession of terrifying dreams, a young American boy is faced with the strange truth that his consciousness has become intertwined with that of Big Tooth, his Mid-Pleistocene ancestor. Through this dream memories, he relives Big Tooth's life - a life as one of the Folk race, without developed language, social structure or fire. He witnesses Big Tooth's friendship with the loyal Lop Ear, their extraordinary adventures as they journey far from the sanctuary of their cave, his growing romance with the Swift One, and his enmity with the brutal and atavistic Red Eye and his self-enforced reign of terror in their small community. He sees, too, the Folk's fierce battles against the primitive Tree People, and the more advanced Fire People, who, with the use of their bows and arrows, will eventually be the Folk's downfall.