4. 73 Yards
A ghost story, political drama, and companion solo story all at once, "73 Yards" is a strong episode that allows audiences to get to know Ruby outside of her interactions with the Doctor. After disturbing a fairy circle, Ruby found herself abandoned by the Doctor and pursued by a mysterious woman who was always precisely 73 yards behind her. Although the episode originally seemed to draw on folk horror, it eventually turned into a tragedy, as everyone she cares about rejected her after speaking to the woman.
The main highlight of this episode was how well it showed off Ruby's struggles with abandonment. As more and more people left Ruby, she became closed off and lost the ability to connect with people properly. This is a great character exploration, which connects the beginning and the ending of the season together.
Unfortunately, while most of the character beats work well, the plot itself has some pretty major holes. There is very little internal logic to how the mysterious woman works, and Ruby allows horrible things to happen to other people before she's willing to take action. "73 Yards" ultimately ends up being an episode that is enjoyable to watch, but falls apart under sufficient scrutiny.