When a family of nomadic Cro-Magnon men encounters some cave-dwelling Neanderthals, the details correspond to known anthropological data; ""practically all the rest is guesswork, "" acknowledges the archaeologist author. His interpolations seem highly plausible: guarded cordiality on both sides marks the initial confrontation, followed by gradual acceptance of differing habits and languages (the children learn fastest) and growing intimacy between individuals. Misunderstanding generates the death of all the Neanderthals except one female who is then accepted by the Cro-Magnon in a simple tribal ceremony absolving them of blood guilt. Integration of the plot with anthropological information is effected in this narrative, but the characters are necessarily sketchy and the prehistoric mind remains distant.