Johnstone of the Border by Harold Bindloss

It was one o'clock in the morning, but Andrew could not sleep. He sat by an open window, looking at the tops of the firs, which stood out in black silhouette. It annoyed him to be so wakeful, as he and Whitney were to make an early start for Edinburgh; but Andrew had something to think about, for he realized that his friendship with Elsie could not be resumed where it had broken off. She had grown up while he was away, and his feeling toward her had changed. To be regarded as an elder brother no longer satisfied him, and if he were not very careful, he would find himself in love with her. This was unthinkable: first of all, because he was lame and poor, and then because it was obvious that Elsie ought to marry Dick. She had no money; Dick had plenty and, besides, Dick needed her. Elsie would keep him straight, and his weak heart would cease to trouble him when he steadied down. Andrew had long cherished an affection for both of them, and he knew that Dick trusted him.

Then he reflected that Elsie's attitude toward Dick was to a large extent protective and motherly, which was not the feeling one would expect a girl to show for the man she meant to marry; and while Dick was obviously fond of her, his attachment, so far as one could judge, was not passionate. Besides, when one came to think of it, the suggestion that their marriage must be taken for granted had come from Staffer. He had, so to speak, delicately warned Andrew off.