I looked at a house to buy a few years ago. Amazing specs, great price - and it was indeed a beautiful house.
The agent was a bit cagey about it, and when we got there for a viewing, we discovered why: it is a terraced house, and the neighbour that shares one wall with the property has been walled in for 20 years. Nobody has seen him or her for all that time - but s/he is definitely in there.
The doors and windows are nailed shut from the inside. The local social services post food through a big vertical letterbox on the front door. Not sure how waste was disposed of, or whether it just gathered inside.
My then-wife and I had the notion that one night an ax would come through the shared wall and a dusty maniacal face would appear, cackling madly - so to counter this, we conceived of a Scooby Doo scenario where we dressed up as ghosts to make them drop dead, then buy the house cheap and knock through…
In the end it was just a little too expensive for us, and had failed two surveys, so we didn’t go for it. Shame. It would have been quite cool to live next door to a crazy recluse.