He tells the ending of the story first, and then explains how it happened so that the reader knows the emotions colonel Owens feels after their escape.
Explanation: Charles Chesnutt gives a general idea of how the characters end up at the beginning of the story so that the reader is aware of where is everything leading up to. He then tells the journey of the Colonel's son and the slave he saved; Grandison, since he looked trustworthy to the Colonel. After a series of events, the author chooses to finally reveal how unfortunate the Colonel feels after catching a glimpse of Grandison and his family escaping on a boat.