At last! Bill in action! It’s about time Bill had some responsibility and agency. In this episode she does it all with a vengeance.
Bill’s choice to put the Doctor’s needs over conventional wisdom (though she rightly planned on the Doctor eventually saving the world, as one does), reveals the powerful familial relationship between them. Who hasn’t made an irrational choice to put family over the needs of other’s? (For good or bad…)
Bill chose to save the Doctor with the power she had in a way that she didn’t have to save her mother. This ability to back in time and keep them alive is a common fantasy for people who lost their parents as children. We watched this fantasy play out before on Doctor Who in Paul Cornell’s episode, Father’s Day. I believe that same need drove Bill to save the Doctor, though in Bill’s case it was an example of displacement (“satisfying an impulse…with a substitute object“) rather than wish fulfillment. She saved the Doctor because she couldn’t save her mum.
More subtly, we see the Doctor also engaging in the family dance. In his case, his refusal to trust and rely upon Bill and tell her about his blindness sets-up the major crisis of the episode. As we have watched since Knock Knock, the Doctor is overprotective of Bill, willing to sacrifice for her, but reluctant to burden her with his needs. So, when he needs to read a ridiculous and unnecessessarily archaic scroll lock, he is alone and unable to save the world, forcing Bill to do so.
Every year at this time I have patients graduating from High School and preparing to leave home for college or other adventures in growing-up. A standard part my treatment with graduating seniors is how to manage their parents, who are slowly going crazy, usually by regressing to forms of parenting they used when my patient was 12. It is hard to believe your child is capable of navigating the world without you. The Doctor is not immune to this. One thing I tell the parents when we inevitably have a session with the whole family (in an attempt to restore sanity) is that you create that of which you are most afraid. Treating your eitheteen year old like she is twelve because you are so afraid you going to lose your relationship with her when she goes off to college is an excellent way to lose her when she goes off to college.
If the Doctor doesn’t stop protecting Bill in an effort to not lose her, he’s going to lose her anyway.