A really enjoyable Susan side-story. It gives her some action to work with, shows her make a personal connection, and proves her strengths when on her own. It is not a mind-blowing new concept or anything like that, but it is a story about character, and I value that a lot.

Is it perfect? No. The villain is ridiculously one-note, and it leaves some large-scale issues open at the end, but it sets out what it wants to achieve and, in my eyes, is the clearest example of Susan being the Doctor’s granddaughter.