He tried to discover what the computer’s other mental block was all about, but it seemed, not unnaturally, to have a mental block about it. He could no longer find any trace of it at all, in fact; it was that good. He wondered if he had been imagining it. He wondered if he had been imagining that it was something to do with something in the building, and something to do with the number thirteen. He ran a few tests. Yes, he had obviously been imagining it.
