Ghost Light is my favourite Doctor Who story and absolutely everything in it makes sense. Give it another watch, there's a lot to soak up but the explanations are all there.
Absolutely everything? I understand the basics, but maybe you can help me; why is Mrs Pritchard stimulating Control with copies of The Times
? Why does the snuff box glow with Light energy? Why are Mrs Grose and the day staff even retained? Why do the night maids disappear without explanation?