Allusion - Macbeth

"Can I give you a challenge?" You are familiar with her now. You can tell she enjoys having her knowledge tested.
"Of course! Anything you'd like."
"Find a Shakespeare reference in 60 seconds. Ready...set...go!"
She easily thumbs through the novel, and after only 15 seconds she spots a Shakespeare allusion.

--
"'Yes - 'after life's fitful fever they sleep well''" (Bronte 108).
--
You can't help but be impressed. "That's from Macbeth, right?"
"Someone knows their Shakespeare," she praises you. You enjoy seeing her smile.
"Well, high school English classes make Shakespeare pretty hard to avoid. I don't quite understand where this allusion fits into the story, though."
She elaborates,
"Jane and Mrs. Fairfax were discussing a possible haunting in Mr. Rochester's mansion, Thornfield Hall. Mrs. Fairfax explained that "the Rochesters have been rather a violent than a quiet race in their time..." and therefore they should be resting peacefully in their graves (108). Jane agrees, quoting a line from Shakespeare's Macbeth, "'After life's fitful fever he sleeps well'" (Crowther).  Although she has slightly
modified the line, it is apparent that it stems from Macbeth."

Bronte, Charlotte. Jane Eyre. New York: Signet Classics, 2008. Print.
Crowther, John, ed. “No Fear Macbeth.” SparkNotes.com. SparkNotes LLC. 2005. Web. 3 Feb. 2013.