Ruth had brought a pizza home, and she pigged out, studying for a chemistry exam Friday morning. Finally, when she had actually memorized the last chapter, she glanced up at the clock and realized she had to get some sleep. No point going into an exam groggy. She brushed her teeth, used the bathroom, and crawled into bed. It seemed to her that she was instantly asleep.

Then the dreams began, wild dreams! She dreamt she was a freshman student, in Gibson dorm, and her roommate had left to go home for the weekend. The roommate lived in Cleveland. Ruth didn't know how she knew that. She dreamt that she...