Sonia, Sofya Semyonovna Marmeladova, is the daughter of the drunken civil servant Marmeladov. To support her consumptive stepmother and her three small half-siblings, she lives by the Yellow Ticket of prostitutes. She is the person to whom Raskolnikov confesses the crime before any authority, the one who reads him the resurrection of Lazarus, and the one who follows him to Siberia.
The reader first meets her through her father's account in the tavern: she went out one afternoon, after her stepmother ironically told her to go, and came back with thirty rubles; now she lives in a rented room in the building of the tailor Kapernaumov and hands over to the family what she earns. When Luzhin publicly accuses her of theft, it is Katerina Ivanovna who defends her, shouting that she "sold herself for us."
Sonia never argues with Raskolnikov. On the night he asks for the reading of Lazarus, she answers, when he asks whether she prays much: "And what would I be without God?" Upon hearing the confession, she kneels, embraces him, promises to follow him, and gives him an order: "Go now, this very instant, stop at a crossroads, bow down, kiss first the earth you have profaned." He refuses for now, and she offers him the cypress cross.
In the Epilogue, she follows his convoy with the money Svidrigailov left her, writes to Razumikhin every month, and is loved by the prisoners, who call her "our mother." Readers see her in two ways: as the agent of salvation, whose life refutes a thesis without arguing, or as the figure whose conversion of Raskolnikov the book announces without demonstrating. Among convicts guilty of worse crimes, she is the woman accepted by all who never formulated an idea.