The Prefect Sempronius wished Agnes to marry his son, and on Agnes' refusal he condemned her to death.
As Roman law did not permit the execution of virgins, Sempronius had a naked Agnes dragged through the streets to a brothel.
Various versions of the legend give different methods of escape from this predicament. In one, as she prayed, her hair grew and covered her body. It was also said that all of the men who attempted to rape her were immediately struck blind.
When led out to die she was tied to a stake, but the bundle of wood would not burn, or the flames parted away from her, whereupon the officer in charge of the troops drew his sword and beheaded her, or, in some other texts, stabbed her in the throat.
Agnes is depicted in art with a lamb, as her name resembles the Latin word for "lamb", agnus.