Edgar Demarnay introduced Monty and Sophie to each other many years ago. Though Sophie married Monty, Edgar never ceased to be in love with her and wrote her several letters throughout the years. When he found out Sophie had died he rushed to Monty's house, seeking to relieve his grief by speaking to someone that had known her.
At Lockets (Monty's place), he is introduced to Harriet, and falls in love with her. He also becomes acquainted with David. He tries to persuade Harriet to leave Blaise, and tells her he wants to marry her, but she naturally refuses.
Edgar suffers a kind of transformation at the end of the story. Harriet dead, he has lost both women he loved (her and Sophie). His uncorresponded love now turns to Monty and David. He hoped to have Monty live with him, and more or less adopts David.
Then, all of a sudden, he changes back again, as three women suddenly come into his life.