These three letters, which Emily Dickinson drafted to a man she called "Master," stand near the heart of her mystery. Although there is no evidence the letters were ever posted, they indicate a long relationship, geographically apart, in which correspondence would have been the primary means of communication. Dickinson did not write letters as a fictional genre, and these were surely part of a much larger correspondence yet unknown to us.

In the week following Dickinson's death on May 15, 1886, Lavinia Dickinson found what she described as a locked box containing seven hundred of her...