Before I did this, I was looking up to see the prompts I gave, and I hereby promise not to give you one about an SF show with a Shakespeare obsessed serial killer again. *cough*

Anyway, this is a little vague as a prompt, but what if there's a literal ghost train network along all the disused/closed railway lines, (of course, incorporating lost Underground stations, too). And the people who know about it and, er, have to guard the secret/use it for stuff/haunt it. Anyway "ghost train network", whatever you can do with that.