Ian travels to the Dalek's mine in Bedfordshire, Susan and David travel through the sewers of London, and Barbara and Jenny escape from London.
Good old Terry Nation and his episode titles that have no bearing whatsoever on the plot. "The End of Tomorrow" is a striking title though. William Hartnell is absent from the episode, which definitely makes the episode less enjoyable.
Each of the leads have separate storylines. Barbara's takes up the least timel but it's fun to see her driving a tanker through a group of Daleks.
Ian has found a friend in Larry Madison, played by Graham Rigby. Rigby is very good as Larry, a character who you know won't survive until the story's conclusion. It's also nice to see a pre-Are You Being Served? Nicholas Smith appears briefly.
Susan and David spend most of the time wandering through badly lit sewer sets. It's padding, pure and simple, and serves no other purpose in the plot other than to reunite them with Carl Tyler. There's a nice action sequence with Susan almost getting eaten by an alligator.
Overall, the episode's fun, but everything's rather inconsequential to the plot.