There was a Point Horror book that I read as a lad about some guy looking for a missing girl. And then it turns out that there had been loads of missing children in that city over the previous few years. It turned out they had gone feral and were luring other kids away to form a weird tribe thing in the sewers and storm drains. I vaguely remember they were in tattered clothes and had really long claw like fingernails.

It properly messed me up and any references to going underground set me on edge for a month or two. I'm laughing at what a dumb kid I was as I remember this but even Jamiroquai's song Deeper Underground was a worry. Like, not the song itself because it wasn't about a cult of wild animal kids that want to claw me up that lives underneath the earth (it should've been!) but just the phrase itself was a kind of trigger. Bless xD

Now though I love the idea of things beneath the earth. I'd bloody love to read that book again but alas will never be able to find it or remember its name.

EDIT: Aha! https://www.amazon.co.uk/Vanished-Ce.../dp/1407110608