4 ideas
Omelas is a joyous, free city without kings, slaves, or guilt, celebrating a summer festival, yet its entire happiness depends on one feeble-minded child kept naked and filthy in a locked basement closet, never spoken to kindly. Every citizen is shown the child once they are old enough; most weep, then rationalize and stay, but a few leave alone at night, walking out of the city toward a place the narrator cannot describe.
The child's misery is not hidden from the citizens but deliberately revealed to each of them. That turns the arrangement from an accident into an informed collective choice: anyone who knows and stays is endorsing the trade, so innocence is not available to the beneficiaries. The story suggests the citizens' depth, compassion, and art are partly produced by living with this knowing acceptance.
The narrator invites readers to add whatever details make Omelas believable to them, such as drugs, technology, or orgies, arguing that we trust pain more than joy and treat happiness as naive. The child arrives only after the reader has built a paradise they can accept, which suggests that some cost is what makes paradise credible. The reader becomes a co-author of the bargain rather than a judge of it.
The ones who leave neither free the child nor reform the city, because freeing the child would destroy Omelas's happiness and the child is too damaged to benefit. Their refusal is simply to stop benefiting from the suffering, and they head toward a destination that cannot be described, not a better system. This defines moral exit as rejecting an unjust bargain even when you have no workable replacement to offer.