Lindy Pepper-Bean (Callie Cooke) lives in Finetime, a city of white, wealthy young adults from Homeworld, shielded from the deadly Wild Woods that surround them. They are united by a social media interface, which is literally a bubble around their heads, projected by Dots, or robots that control their movements. Lindy is not bothered by the fact that a number of her friends are missing. When the Doctor (Ncuti Gatwa) tries to send her a warning, she blocks him out. Ruby (Millie Gibson) appears in Lindy’s bubble and coaxes her to drop it. She sees some giant slug-like creatures eating some of her neighbors, but she ignores them.
The Doctor and Ruby show Lindy and her friends how to evacuate Finetime through conduits leading to an underground river. Lindy is surprised that Ruby and the Doctor are a team> Lindy sees a message from her mother Penny (Susan Twist), who is known to the Doctor and Ruby, but from different places. Lindy is helped by Ricky September (Tom Rhys Harries), whom she idolizes. He tells her he turns off his bubble now and then and can live without it. He knows Homeworld is being consumed by slugs but assures her that everything is fine.
The Doctor realizes that the slugs were bred in Finetime by the Dots, and that they kill the residents in alphabetical order by surname. Lindy can no longer control her Dot when it attacks them. Lindy is cornered and reveals Ricky’s birthname was Richard Coombes and leaves him to be killed by the Dot. She meets with the few remaining residents and lies to them about it.
The Doctor offers to take Linda and the other survivors away in the TARDIS, but they refuse, apparently because they are racist. He warns them they will die if they stay and begs them to let him save them. They refuse and set off in a boat on the river. The Doctor and Ruby leave in sorrow and anger.
The episode was written by Russel T. Davies with the help of Steven Moffat, originally for Eleventh Doctor Matt Smith and Amy Pond (Karen Gillan). But it was rejected because it was too expensive. Disney now oprovides more funding. Dylan Holmes William directed. It took three people to animate the slugs.
It got 93% on Rotten Tomatoes. Doctor Who seems to get a lot of love from them, I think because it is so different from everything else on TV. As in some other early episodes, Ncuti Gatma was a bit of a no-show in this episode because he had just been hired and still had other acting commitments to attend to.