The story is about an article about Uqbar that a friend of the author finds. They search for it in the Encyclopedia Britannica but they do not find the article. Later, the friend of Borges shows him the main article, which is not even in the index of the encyclopedia. Borges later finds whole new articles about Uqbar, Tlön and Orbis Tertius. The author apears to have entered another world in which strange things happen.
Those strange things are:
- There is no causality
- There is no materialism: everything is mental or spiritual
- Objects not observed for a long time simply disappear (similar to the ideain quantum mechanics that photons come into existence and take a position and a momentum when they are detected)
- Lost objects reappear duplicated and with different characteristics