But suddenly her laughter broke flatly and she reined in the mare.

Sheldon glanced at her sharply, and noted her face mottling, even as he looked, and turning orange and green.
"It's the fever," she said.

"I'll have to turn back." By the time they were in the compound she was shivering and shaking, and he had to help her from her horse.
"Funny, isn't it ?" she said with chattering teeth.

"Like seasickness--not serious, but horribly miserable while it lasts.

I'm going to bed.