A flashback occurs in "The Lady of the Tiger?" just as the handsome youth enters the arena to make his terrible decision between the two doors. In the moment that he turns and meets the eyes of the princess, Stockton cleverly flashes back to a time prior to the arena day; the narrator informs the reader that the princess has used her wiles to uncover the secret of the doors--and not only the secret of the doors--but also the name of hte lady behind the door. This well-timed flashback increases the suspense of the short story, because the reader learns that the princess feels incredibly conflicted about her choice, due to the lady's identity.
Stockton uses his well-placed flashback to increase the suspense of the princess's internal conflict which will ultimately decide the outcome of the story.