John Eyre, Jane’s uncle, has a substantial impact on the novel without ever actually appearing in the text. Readers know very little of him—only that he went to seek his fortune in Madeira. We first hear of John when Bessie tells Jane that he tried to visit her at Gateshead while Jane was at Lowood. Later, Mrs. Reed reveals that he also sent a letter, in which he expressed a desire to adopt Jane and bequeath her his fortune, but that Mrs. Reed selfishly kept it for three years without passing it along to Jane. It is John Eyre who sends Mr. Mason to break up Jane and Mr. Rochester’s wedding, before ultimately dying and leaving Jane twenty thousand pounds and the knowledge that she is related to the Rivers family.
John Eyre’s character, then, exists exclusively to resolve issues of plot. He is essentially a deus ex machina—that is, a plot device where an unlikely event or character suddenly appears to resolve a seemingly insurmountable issue—or, in the case of Jane Eyre, several issues. John is responsible for exposing Mr. Rochester’s past, he provides a family for a woman who thought that she was alone in the world, and his death gives Jane enough money to put her and Mr. Rochester on more equal footing.