This is a pretty mediocre story. It's clear that the writers made this episode arc to develop the characters as the story is not original nor unique.
The Doctor and the gang travel back in time to early modern times. It's supposed to be prehistoric times, but due to budget problems and inconsistencies with the guest cast, you'd never quite believe it was so.
The Doctor and the group by a clan of caveman and cavewoman who illogically speak pretty good English!!! Good English not withstanding, they took the group hostage. We see there is trouble within the clan itself as several people are vying for power.
As mentioned, it's rather an uninspiring story after the entertaining pilot. Gladly the story would improve after this dreadful start with the introduction of the Daleks, but this story arc with the clan isn't really the best of the William Hartnell years. This story arc drags for about three episodes, but this is more like a two episode parter. The only things that stick out are that we get more information about the Doctor and Tardis, how he despite him being a Timelord doesn't quite have control over time and balance.