On a ringworld or orbital or similar mega-structure of the far future communities are voluntarily separate, pursuing their own visions of agrarian paradise. Such communities have become increasingly insular and inwards looking. They are not ignorant of the technological backgroup to their civilisation, they just choose not to engage with technology at this level.

There is a murder in a village.

Everyone has some dirt on someone: normal small town politics. No one trusts anyone else to get to the bottom of this in a non-partizan fashion.

Only the Knife Sharpener, an itinerant worker who travels between these communities has the objective distance to conduct the investigation. But he too is distrusted, as a gypsy might be distrusted.

What am I saying here? That humans are inherently corrupt. That reducing technological complexity in society is balanced by increased behavioural complexity. That ideal societies are impossible.