All this I knew; it was not until I was ordered East at the close of the European war that I knew something else — that I loved Sophia and that I wanted to marry her.
-- Narrator (Chapter 1)

Importance: Charles gets involved in Sophia’s life and the murder of her grandfather because he wants to marry her. He had decided that he wanted to marry Sophia even before he knew anything about her family.

I began to feel, uneasily, that something was the matter — something, I mean, other than the first natural awkwardness of meeting again. There was something wrong, definitely wrong, with Sophia herself.”
-- Narrator (Chapter 2)

Importance: When Sophia and Charles meet for the first time since they were in Egypt together, Charles senses that something is wrong. At first, he thinks that it is stress in their relationship but comes to realize that there is something wrong with Sophia, in her personal life.

It...
-- Sophia (Chapter 2)