 Why did Simon's new friend not give him an aspirin when Simon asked for one?
He sat down at his desk, passed his tongue over his teeth in distaste, groaned, fumbled in a drawer for the aspirin bottle. He looked over at Betty and said, almost as though reciting, "What I need is a vacation." "Providence," Simon told her whilst fiddling with the aspirin bottle, "will provide." Something where you could deduce that actually the ruby ring had gone down the drain and was caught in the elbow. Simon said, enigmatically, "Now it comes." The client fussed himself with Betty's assistance into the seat, bug-eyed Simon, said finally, "You know my name, that's pretty good. When Simon continued to say nothing she ventured, "Time travel is impossible." "Then you'll realize that there are a dozen explanations of the paradoxes of time travel. It's my contention that within a century or so man will have solved the problems of immortality and eternal youth, and it's also my suspicion that he will eventually be able to travel in time. "The usual explanation, Betty, is that they can't afford to allow the space-time continuum track to be altered. If, say, a time traveler returned to a period of twenty-five years ago and shot Hitler, then all subsequent history would be changed. Mr. Oyster returned his glasses to their perch, bug-eyed Simon, but then nodded. Simon said, "You want to hire me to find a time traveler and in some manner or other—any manner will do—exhort from him the secret of eternal life and youth, which you figure the future will have discovered. People would figure they had D.T.'s." If you could go back a few thousand years, the things you would wish to see would be a Roman Triumph, perhaps the Rites of Dionysus, or one of Alexander's orgies. You can take the plane to Munich, spend a week there and—" Simon was shaking his head. It goes like this:" I got a thousand dollars from Mr. Oyster (Simon began) in the way of an advance, and leaving him with Betty who was making out a receipt, I hustled back to the apartment and packed a bag. It takes roughly seven and a half hours from Gander to Shannon and I spent that time dreaming up material I could put into my reports to Mr. Oyster. Between Shannon and Munich a faint suspicion began to simmer in my mind.
 He needed to knock him out to go back to the festival so that Simon would not know what had happened.
 He had run out of aspirin and did not know how to help.  The friend thought Simon needed to deal with his headache like a man.  He needed to knock him out to go back to the festival so that Simon would not know what had happened.  He gave him a different medicine instead that he thought would work better.