Moebius is set in the tunnels under Buenos Aires, deep within its labyrinthine subway system, and centers on a metro-train containing 30 riders that has mysteriously disappeared (much like political dissidents tended to "vanish" in Argentina during the yers of dictatorship). The citis subway officials are greatly troubled and so call in a topographer/mathematician to help them find the train. The mathematician soon discovers that the subway system, with its countless add-ons over the years, has become so incredibly complex that a gigantic moebius strip has been created on which the missing train is now trapped in a fourth dimension.

Adapted by Fassbinder from Alfred Döblin's classic 1929 novel of the underclass in Berlin during the Weimar Republic, this is not merely Fassbinder's longest and most ambitious film: it represents the crowning of the director's lifelong obsession with Döblin's novel and is considered by many to be his greatest film. Fassbinder identified closely with his protagonist, released murderer Franz Biberkopf, and of central importance to the plot is Biberkopf's intense friendship with another man.