Why does Linda have to die?

Linda was terminally ill.

"You mean, of her not dying?" (He nodded.) "No, of course there isn't. When somebody's sent here, there's no …" Startled by the expression of distress on his pale face, she suddenly broke off. "Why, whatever is the matter?" she asked. She was not accustomed to this kind of thing in visitors. (Not that there were many visitors anyhow: or any reason why there should be many visitors.) "You're not feeling ill, are you?"