Novella about Domed city with advanced infiltrator

Question

This is a SF novella I read in the late 1980s in the UK.

There is a domed city where people went for refuge generations earlier, the predicted apocalypse never happened but they're unaware.

The outside world, now quite advanced, finally finds a way through the shield barrier and sends one person through, to both make contact and to prepare the lost society for culture shock.

The person, a woman, arrives in the middle of the night, so she has a walk around to pick up cultural clues, she comes to a scary conclusion so hides before daylight.

It seems the cut-off society has had a race war during its history and killed all people of colour, unfortunately the infiltrator is African American and will be slaughtered on sight.

She has a year to survive before the outside people stop the dome shield to make contact, they assume that, by that time, a fully prepared society will be keenly waiting for them.

All she can do is creep around at nights and leave bits of graffiti to try and prepare/enlighten the dome peoples. And hope she can last the twelve months.

Answer 1

I've found this, 16 months later!

"A Scarab in the City of Time" by Marta Randall.

The background for this story is rather complex. In the far future, people who left a dying Earth return to find the few remaining folks on the planet living in a domed city, cut off from what they think is an unlivable world. The narrator managed to tunnel her way into the city to study its inhabitants, and can't get out. The story actually begins with the narrator acting as a sort of prankster, leaving graffiti everywhere and messing with the city's environmental controls in an attempt to get the inhabitants (and herself) outside, where it is now safe to live. Written in a very fast-paced, feverish, present tense style.

The narrator, in her night time skulking, finds old records of a race war in the city.

Extract from the ebook:

" The books of the City tell of the battles fought, of the expulsion of the black vermin and yellow lice. If I showed my brown face and epicanthic eyes, my bush of light brown hair, they would stopper my mouth with death before I had a chance to speak"