The theme of the vicious cycle of evil is central to The Witch of Edmonton. Whether motivated by material gain or revenge, several characters in the play choose to perform immoral actions. These have far-reaching consequences that lead them into further immorality, thereby creating a vicious cycle of deepening evil and moral degradation.

The two major plots in the play are driven by this theme. Frank Thorney finds that a small immoral action—sleeping with Winnifride outside wedlock—begins a chain of events that spirals outside of his control. He secretly marries her to save her from societal censure for having a baby out of wedlock, but this decision lays the ground for his subsequent ill deeds. Having married Winnifride without his father’s permission, he is then pressured into a bigamous marriage of his father’s choice. Frank does not anticipate the depth of his second wife’s affections for him, which makes her reluctant to part from him. He murders her out of frustration, afraid that she will discover his secrets, and this is the climax of his path of moral corruption. Frank feels that he is swept in events that have snowballed beyond his control: He says he has “waded deeper into mischief / Than virtue can avoid.