In the first section, Döblin introduces the book’s protagonist, a released convict named Franz Biberkopf. His period of incarceration has made him accustomed to living in confinement and with strict rules of behavior. On his first days in Berlin, he does not cope well. Franz has periods of intense nerves as he dodges the traffic and tries to hide in passageways. He has constant flashbacks of his life in prison, imagining the guards are still controlling his every movement and every sound he makes. Suddenly realizing that he is truly free of those restrictions, he bursts out singing.

He was in a deep dark courtyard. He stood beside the dustbin. And suddenly he started singing in a resonant voice, singing towards the walls. He took his hat off, like an organ-grinder. The echo resounded from the walls. That was fine. His voice filled his ears. He sang in such a very loud voice, he would never have been allowed to sing like that in prison.

The next section provides an overview of Alexanderplatz: the various streets that feed into it, the train station, the kinds of businesses located there, and the overall constitution of the neighborhood. Döblin gives an impression of various activities through devices such as lists of every business on a block or a random sampling of conversations that might be overheard. For example, he offers a snippet of such exchanges for people at the Settin train station, where trains from the Baltic Sea arrive.

Why, you're all covered with soot—yes, there is a lot of dust here.—How do you do? So long—Has the gentleman anything to carry, 50 pfennigs.—Your vacation certainly did you a lot of good.—Oh, that tan will come off soon.—Wonder where people get all the money from to travel around like that.

The complex rhythms of city life—including the intermingling of commerce, socializing, and politics—all feature in Döblin's multilayered descriptions. The reader is gradually introduced to the idea of political unrest as part of the daily discourse. The author apparently assumes the reader will be familiar with the events and people, so much of the content is simply presented without explanation.

Liquor shops, restaurants, fruit and vegetable stores, groceries and delicatessen, moving business, painting and decorating, manufacture of ladies’ wear, flour and mill materials, automobile garage, extinguisher company . . . German fellow-citizens, never has a people been deceived more ignominiously, never has a nation been betrayed more ignominiously and more unjustly than the German people. Do you remember how Scheidemann promised us peace, liberty, and bread from the window of the Reichstag on November 9, 1918? And how has that promise been kept?

Gradually, the focus narrows to a single building, which is a house on Linienstrasse where we had earlier found Franz. Döblin tells us about the offices and apartments that are contained in the building. On the first floor, there is a shoe store and an attorney’s office; the author introduces both the attorney and his charwoman, drawing a contrast between their relative wealth and poverty. On the upper floors are apartments. We are introduced to characters who have various ordinary jobs, such as a waiter who lives with a woman on the third floor.

The waiter is at home all day till two, he sleeps till then, and plays the zither, while lawyer Löwenhund in a black gown dashes around the District Court . . . The waiter's girl-friend is supervisor in a department store. So she says. This waiter, during his married life, was disgracefully deceived by his wife. But she was always able to console him until he finally walked out . . . Then he got to know the present one in Hoppegarten, where she was out man-hunting. The same brand of woman as the first, only a bit cleverer.