where a sheet of paper could have been mislaid, taking all his
books, one by one, from the shelves and leafing through them, even
books he knew he had not touched for more than three years. In the
end, he sat down again at his desk, defeated. The note on the _Kilroy_
simply did not exist.

Of course, that didn't settle it, as finding the note would have. He
remembered--or believed he remembered--having gotten that item of
knowledge--or delusion--in 1970, shortly before the end of the school
term. It hadn't been until after the fall opening of school that he
had begun making notes. He could have had the knowledge of the robot
rocket in his mind then, and neglected putting it on paper.

He undressed, put on his pajamas, poured himself a drink, and went to
bed. Three hours later, still awake, he got up, and poured himself
another, bigger, drink. Somehow, eventually, he fell asleep.

* * * * *

The next morning, he searched his desk and book-case in the office at
school. He had never kept a diary; now he was wishing that he had.
That might have contained something that would be evidence, one way or
the other. All day, he vacillated between conviction of the reality of
his future knowledge and resolution to have no more to do with it.
Once he decided to destroy all the notes he had made, and thought of
making a special study of some facet of history, and writing another
book, to occupy his mind.

After lunch, he found that more data on the period immediately before
the Thirty Days' War was coming into his consciousness. He resolutely