The following quote is from a a 17th century story written in vernacular Chinese:
The English translation is as follow:
The story is about a man named Jiang De, also known as Jiang Xingge, a native of Zaoyang County in Xiangyang Prefecture, Huguang Province.
The entire sentence after the first comma makes perfect sense to me. With that in mind, I assume 话中单表一人 to mean something a long the lines of "In our story, there is a man". However, I can't really figure out what 单 and 表 function in this sentence, and whether they are connected or not. The closest I can get is 单 to mean only and 表 to express, as in "In this story we focus on telling about a man", but that does not feel right.