In Charlotte Brontë's novel, Jane Eyre, the bedroom fire is a key incident in the plot surrounding Bertha, the mad wife who Rochester keeps locked in his attic. The key plot issue the novelist faces here is trying to make Rochester an appropriate husband for Jane, and making the reader sympathetic to their romance. Rochester, after all, is married to one woman, had a French mistress, is courting Blanche, and is flirting with Jane, and is thus a rather confirmed libertine.
The fire in the bedroom functions two ways in the plot. It serves to put Bertha in a bad light (as she is trying to kill Rochester) and gives a second incident in which Jane rescues Rochester. The use of the term fairy, in fact, is related, inter alia, to Jane's opportune rescues of Rochester (when they first meet and during the fire). She acts like a "good fairy" or guardian angel to Rochester.
The fire in the bedroom also foreshadows the fire towards the end of the novel, also set by Bertha, in which Thornfield is destroyed and Rochester burned and blinded.
In each of these fires, Rochester is changed morally. Thus fire appears also in its symbolic aspect as something that purifies, both in the alchemical sense of removing impurities and in the sense of "trial by fire".