With close reference to chapter 20, explore Brontë's success in creating suspense.

The suspense that builds in Jane Eyre is meant to create mystery and ambiguity around the setting of Thornfield Hall, Mr. Rochester's family home, which houses his mad wife, Bertha Mason, in a hidden room. Jane begins to notice the strange behavior of Grace Poole, one of the servants of the house, but she becomes distracted when Mr. Rochester brings home a party of visitors. During this visit, an uninvited man named Mr. Mason arrives. His presence clearly disturbs Mr. Rochester, as Mr. Rochester admits to Jane that he is worried he would be judged by the guests if they were to learn certain things about him. In chapter 20, the house has quieted down, and Jane is awoken from her sleep by a beam of moonlight. Once she is awake, a series of strange things happen to create confusion and mystery in the plot.
First, Jane hears a scream:

Good God! What a cry! The night—its silence—its rest, was rent in twain by a savage, a sharp, a shrilly sound, that ran from end to end of Thornfield Hall.

In the commotion, Jane can hear someone calling for Mr. Rochester to come. Everyone floods from the bedrooms, and Mr. Rochester lies to them all, saying that a servant has had a nightmare. Once everyone is in their rooms again, Mr. Rochester comes for Jane and whispers a request for help, adding a question about how she handles the sight of blood. These details, paired with Mr. Rochester's stated fear from chapter 19, verify that he has a secret, and the anticipation builds as we, with Jane, follow him to the forbidden rooms on the third floor.
To add to the suspense, Grace Poole and Mr. Mason, the two most mysterious characters, are in the room where Mr. Rochester brings Jane, and we believe we are about to get some answers, only to discover that Jane will be left alone with Mr. Mason to sponge his mysterious neck wound in silence while Mr. Rochester is busy getting help. While Jane and Mason are alone, Bronte incorporates some adept repetition and imagery to create a more sinister and symbolic atmosphere:

I must dip my hand again and again in this basin of blood and water and wipe away the trickling gore. I must see the light of the unsnuffed candle wane on my employment; the shadows darken on the wrought, antique tapestry round me, and grow black under the hangings of the vast old bed, and quiver strangely over the doors of a great cabinet opposite—whose front, divided into twelve panels, bore, in grim design, the heads of the twelve apostles, each enclosed in its separate panel as in a frame; while above them at the top rose an ebon crucifix and a dying Christ.

Bronte's extended description of the room, with its religious images and ominous lighting, provides the best source of suspense, since we, with Jane, are waiting anxiously for Mr. Rochester to return or for something terrible to happen, like an attack from the person in the locked inner room. Every detail of the setting extends the wait and gives added indications of danger and discomfort, heightening the suspense with each new image.
With these unnerving surroundings, Jane begins to puzzle together the clues she has about the secret Rochester must be keeping. She wonders about Mason, about what caused his injury, about why they are not allowed to speak; and just as that unsnuffed candle finally goes out, at the moment of highest tension in the chapter, Mr. Rochester returns with help for Mr. Mason. As the doctor is dressing Mason's wounds, Jane hears some more clues about Mason's incident:

"She bit me. . . . She worried me like a tigress, when Rochester got the knife from her."

Jane receives no explanation of this from Mr. Rochester, only an errand to fetch him a fresh shirt. Jane assumes the "she" in Mason's story is Grace Poole, and once they are alone, she asks Mr. Rochester if Grace Poole will continue to live at Thornfield Hall. He says she will and tells Jane not to worry about her, which confuses and perplexes Jane, who is afraid for his life.
Mr. Rochester makes light of the event, teases Jane about keeping him company the night before his wedding, and makes an excuse to visit the servants in the stable; and we, with Jane, are left with more unanswered questions than anywhere before in the plot line. The suspense stays heightened for a while longer in the story, with more events happening in the night, like Jane's veil being torn, and with Jane's nightmares haunting her and giving her apprehension. All these details lead to the revelation of Bertha in the inner room, and the suspense lifts as Jane stands in her wedding gown before Mr. Rochester's first wife, with Bertha's brother, Mr. Mason, having interrupted the ceremony at the church.