As you may guess from the episode title, this one is pretty much all about Jane. After she is left catatonic because of the events of the last episode, the team is concerned with what is going on with her mind. The Negative Man makes a transference of Cliff’s mind into Jane’s, and we are treated to a reveal of how Jane’s mind works and the Underground where her personalities live.
While all personalities can come to the front, there are only certain “primaries” who can easily maintain control for longer periods of time. Some of the personalities look like Jane, while others don’t. Memories made by one personality can be explored by any other personality. Personalities can even kill themselves then, and the areas of the Underground they live in becomes very dark and disturbing. I feel that this has been hinted at already, but it appears that the fracturing of Jane’s mind starts with abuse by her father.
With Cliff’s support Jane is able to confront and overcome a ghost of her past, and is ready to come to the front again, rejoining the team.
Something happened in the real world while Cliff was in Jane’s mind, and I have a feeling that we will find out what that was on the next episode of Doom Patrol.