As Pessoas no precipício por Ian Watson.
A história foi apresentada na coleção Evil Water: And Other Stories . Partes do texto estão disponíveis em o Google eBook versão
A parede vertical é descrita da seguinte forma:
"Just suppose," he said, as the daylight dimmed, "that a whole world is as flat as a leaf! And suppose that creatures live within that leaf, who themselves are perfectly flat. Imagine this narrow ledge here simply carries on" - he chopped his hand into empty space - "in that direction forever! Imagine that it is a simple, infinite surface with nothing above it and nothing below it. And with no precipice to jut out from."
E mais tarde, a sugestão de um personagem de subir para cima parece ser um grande problema, comparado ao que geralmente é feito:
"We make daily forays up and down for food. When we've scalped a patch we migrate sideways. That's life."
[...]
"And you'll die clinging on. Or rather, you'll die pretty soon after you stop clinging on. Now, today I'm climbing up to the Chief-of-Chiefs for that conference. Bounce will guard our ledge and keep the kids tied up. Loosepiton" - that's me - "will escort me upwards."