hen a change in place in a novel is accompanied by a shift in time, most often the device employed by the novelist is not an annex, but a flashback (or analepsis). Anachrony, or the disordering of story events in their presentation, may be a complicating factor in an annex, but a flashback rarely exhibits all of the traits of an annex. When George Eliot's narrator relates the background of Dr. Lydgate, she moves the reader of Middlemarch (1871-2) to the Continent and back in time. The additional shift in genre to the melodrama of Lydgate's infatuation with the actress Laure makes it tempting to consider this episode a narrative annex, but most annexes, like most Victorian novels, unfold without disrupting the consecutive time of the narration. In this instance, the representation of a boundary-crossing is missing, and the narrative content, though it illuminates Lydgate's character, does not make up a kernel plot event. To take an even more extreme example of a flashback that shares some but not all of the traits of a narrative annex, when Sir Arthur Conan Doyle abruptly transports his readers from Sherlock Holmes' London to the Great Alkali Plain in A Study in Scarlet (1887). 
Suzanne Keen. Victorian Renovations of the Novel: Narrative Annexes and the Boundaries of Representation. Cambridge UP, 1998.