They are talking about a story Mr.Wren wrote, a story about a spavined horse.

他在谈雷恩先生写的一故事，一匹破马的故事。

They are not talking about a story Mr.Wren wrote, a story about a spavined horse.

在谈雷恩男士写的唯一古代事件，一匹破马的古代事件。