The speaker is worn out by guilt and is begging for an end to it. The repeated plea, "mercy, mercy, peace," opens and closes the poem's key moments like a prayer said over and over. Fire is the central image. It is usually thought of as cleansing, a way to burn away "every dark thing," and the speaker wants that kind of purification. But the poem also hints at fear: the speaker dreads looking back at their past and imagines being called a liar and a "filthy rat."
The feeling is a mix of exhaustion, shame and desperate hope. The speaker mentions promises and sacrifices, and says they have shut their own "escape door," which suggests they feel trapped. Memories "buzz like bees," restless and impossible to ignore. Still, the speaker wants to come clean and accept the past as it really was. The mood is tense and heavy, yet it ends on a thin thread of hope that the flames might set them back "on track."