Bertha Mason is one of the most iconic literary figures of a woman locked up by her family to contain her emotional outbursts. Jane, too, is locked up by her family in Chapter 2, foreshadowing that confinement of emotional women and family secrets will be a central plot point:
I resisted all the way: a new thing for me, and a circumstance which greatly strengthened the bad opinion Bessie and Miss Abbot were disposed to entertain of me. The fact is, I was a trifle beside myself; or rather out of myself, as the French would say: I was conscious that a moment’s mutiny had already rendered me liable to strange penalties, and, like any other rebel slave, I felt resolved, in my desperation, to go all lengths.
They went, shutting the door, and locking it behind them.
Mrs. Reed has ordered little Jane to be shut in the red-room because she has stood up to John Reed's bullying. The narrator's comparison of young Jane to a "rebel slave" appropriates the experience of enslaved Black people to foreshadow that the specter of slavery will become an important part of the narrative. Like Mrs. Reed shutting Jane away to avoid confronting abusive family dynamics, Mr. Rochester shuts Bertha away to avoid confronting the sins of his colonial ties.
This scene primes the reader for sympathy toward Bertha. Like Bertha, Jane's "mutiny" against someone who has mistreated her makes her look bad. To Bessie and Miss Abbott, Jane worries, it looks as though she has resorted to violence unprovoked. Her interior reality, to which the narrator provides the reader access, makes her physical outbursts against John Reed and against Bessie and Miss Abbott completely understandable. She feels "beside herself" and desperate not to be locked in the room where Mr. Reed died. The room feels haunted to her, and she does not think she deserves the "strange penalties" that are being imposed on her because she stood up to her bully. And yet Jane's resistance does not save her from being confined until she is no longer so outwardly emotional.
The inability of the outside world to make sense of Jane's violent behavior foreshadows the fact that Bertha's violence will be driven at least as much by misunderstood anger with Mr. Rochester as by mental illness. Bertha, like young Jane, has a complex inner reality that explains her behavior. The only real difference between them is that, as Jane's eventual release from the Red Room hints, Jane will learn to discipline her emotions enough to make herself appear sane so that she can escape Bertha's fate.
In Chapter 10, Jane receives a response to her governess advertisement. The candle burns out as she is reading it, foreshadowing that Jane is about to be plunged into darkness by her life at Thornfield:
Here the socket of the candle dropped, and the wick went out.
The candle burns out as Jane is fantasizing about how charming Thornfield will be. It may seem to her like a coincidence (or the idea that the candle burned out at this exact moment may be retrospective embellishment by the narrator). To the reader, the sudden loss of the candlelight is a sign that Jane is seeing a bright future where there may be none: Jane's hopes themselves are about to be extinguished, as they often have been by her circumstances.
Although the whole novel takes place in settings that are common in gothic fiction (a boarding school, a mean relative's house, etc.), Thornfield is a manor house full of rattling and secret histories related to race and ill-gotten wealth. Practically cursed, it is the most unmistakably gothic place in the novel. The candle going out at this moment signals that Jane is about to enter the dark heart of the novel, and that the reader had better start paying attention to how she deals with haunting and horror. The candle also foreshadows that fire itself will be an important force at Thornfield. Jane will extinguish one fire set by Bertha, and another will eventually burn down the entire house.
It is notable that the narrator does not remark upon her own reaction to the candle going out at the time. The younger version of Jane does not seem able to interpret the signs of her impending misfortune in the same way the reader can. This could be an indicator of her naïveté, or it could be another indicator that the narrator is taking artistic license to create suspense for the reader. In reality, the candle may not have burned itself out in this dramatic way.
In chapter 15, Jane hears mysterious noises and finds Mr. Rochester in bed with his sheets on fire. What Mr. Rochester says to her after she douses the flames foreshadows the existence of Bertha, his wife:
‘In the name of all the elves in Christendom, is that Jane Eyre?’ he demanded. ‘What have you done with me, witch, sorceress? Who is in the room besides you? Have you plotted to drown me?’
Mr. Rochester has asked if Jane Eyre is present, so it seems plausible to Jane and the reader that he is speaking to her. Technically, though, Mr. Rochester's speech is ambiguous. When he asks, "who is in the room besides you?" he might easily be clarifying whether it really is Jane Eyre in the room in addition to the person he is addressing. The narrator (and the reader who is returning to this moment for a second time) can see that he likely imagines that he is calling Bertha, not Jane, a witch and sorceress.
It may not be possible to recognize on a first reading that Mr. Rochester is addressing his secret wife. Still, the astute first-time reader may pick up on how Mr. Rochester's confusing accusation contributes to a mounting sense of gothic danger about Thornfield. Jane has tried to rescue the owner of the house (the rescue itself foreshadowing the way she will eventually rescue him from his bad marriage), and he seems to have accused her of trying to kill him. There is an atmosphere of mysterious hostility and ill will about the place that Jane finds intriguing if disturbing: there is a mystery here to be solved. Jane's role as a gothic heroine is reflected in the way she is fascinated by this danger rather than wholly repelled by it. As it turns out, things are much more sinister than Jane imagines. Mr. Rochester's hostility is born out of the fear he holds toward the wife he has locked in the attic. The fact that Mr. Rochester does not distinguish clearly between Jane and Bertha in his sentence structure emphasizes how easily Jane could slide into the role of wife-locked-in-attic. To Mr. Rochester, any angry woman is a potential "witch" or "sorceress" to be restrained. His demonstrated potential to abuse women is why many readers find it disturbing that Jane eventually marries him, reformed though he might seem by the end of the novel. Readers worry that moments like these foreshadow the way he will come to treat Jane after the novel ends.
Before the first time Jane is to marry Mr. Rochester, multiple incidents foreshadow that this wedding is not going to work out. In Chapter 25, Jane delivers a monologue to a chestnut tree that has been ominously struck by lightning:
"You did right to hold fast to each other," I said: as if the monster-splinters were living things, and could hear me. "I think, scathed as you look, and charred and scorched, there must be a little sense of life in you yet, rising out of that adhesion at the faithful, honest roots: you will never have green leaves more – never more see birds making nests and singing idylls in your boughs; the time of pleasure and love is over with you: but you are not desolate: each of you has a comrade to sympathise with him in his decay."
The ruined tree foreshadows that the wedding, too, is about to be ruined by a metaphorical bolt of "lightning," when Mr. Mason suddenly reveals that Mr. Rochester is already married to his sister. "Charred and scorched," the tree also foreshadows the way the entirety of Thornfield will burn down by the end of the novel. Like the wedding, Thornfield is also struck down by Bertha, her supposed "madness," and her refusal to remain locked away in the attic.
More than all of this, Jane's speech to the tree foreshadows how she will weather the tribulations that are to come. "You did right to hold fast to each other," she tells the splinters of what once was a strong trunk. A wedding involves two people promising to "hold fast" to one another. When her union to Mr. Rochester does not work out, Jane will have to imitate the tree in "holding fast" to herself. Though "scathed" by the ruined wedding and deprived of "the time of pleasure and love" she hoped to share with Mr. Rochester, she will not be "desolate." She will rely on the "faithful, honest roots" she has cultivated (the faith she has modeled after Helen's, and the kindness and patience she learned from Miss Temple) to keep her from desolation.
In Chapter 25, the night before her scheduled wedding to Mr. Rochester, Jane has a series of bad dreams and a waking vision of a woman that foreshadow a bad outcome for the wedding. Mr. Rochester tries to convince Jane that the dreams don't mean anything, but Jane insists that it is not all in her head:
"But, sir, when I said so to myself on rising this morning, and when I looked round the room to gather courage and comfort from the cheerful aspect of each familiar object in full daylight, there – on the carpet – I saw what gave the distinct lie to my hypothesis – the veil, torn from top to bottom in two halves!"
It is the morning of the wedding, and Jane has found her veil mysteriously torn in half after seeing a strange-looking woman pull it out of her closet in the middle of the night. Although Mr. Rochester tries to distract Jane by telling her that it is a good thing only the veil was harmed, Jane is clearly onto something with her nerves. In a gothic novel, people might have nervous dreams that are about their own internal anxieties. But those anxieties usually have external causes. As a rule, there are always explanations for things that happen in the physical world. Full-on hallucinations are not common. Jane's veil did not tear itself in half, and it did not tear in half by magic. That is beyond the scope of possibility. Based on the conventions of gothic novels, the reader can expect an explanation before the end of the novel for how this strange occurrence happened and what it means for the future.
Something of course does go wrong on the wedding day: it is revealed that Mr. Rochester already has a wife, and she is locked in the attic. She is the one who has broken into Jane's room and destroyed the veil. It may be hard to imagine, as a modern reader, how Mr. Rochester was planning to keep concealing Bertha from Jane. The answer lies in his status as a landowner in a gothic novel. Houses and their owners in this genre are typically full to the brim with secrets that are gradually revealed over the course of the novel. Mr. Rochester has been holding Jane and the reader in suspense up until this point, and he seems hopeful that he can hold out that suspense indefinitely by convincing Jane that her mind is playing tricks on her. Jane does go ahead with the wedding until Bertha's brother interrupts it, but the confidence with which she reports finding the torn veil suggests that Jane can spot foreshadowing better than Mr. Rochester would like.