 Why does Simon ultimately deny Mr. Oyster's request to go to Oktoberfest?
Unfortunately , there was only one thing he could bring back from the wonderful future ... and though he didn't want to ... Illustrated by Freas Betty looked up from her magazine. "Don't yell at me, I feel awful," Simon told her. 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." "What," Betty said, "are you going to use for money?" "Providence," Simon told her whilst fiddling with the aspirin bottle, "will provide." But before providing vacations it'd be nice if Providence turned up a missing jewel deal, say. Something where you could deduce that actually the ruby ring had gone down the drain and was caught in the elbow. Something that would net about fifty dollars." Simon said, mournful of tone, "Fifty dollars? Why not make it five hundred?" "I'm not selfish," Betty said. "All I want is enough to pay me this week's salary." "Money," Simon said. "Hm-m-m. I didn't know most sleuthing amounted to snooping around department stores to check on the clerks knocking down." Simon said, enigmatically, "Now it comes." Betty bounced up with Olympic agility and had the door swinging wide before the knocking was quite completed. He was old, little and had bug eyes behind pince-nez glasses. His suit was cut in the style of yesteryear but when a suit costs two or three hundred dollars you still retain caste whatever the styling. Simon said unenthusiastically, "Good morning, Mr. Oyster." 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."
 He knows he will not be allowed to do something that might impact the past
 He believes that Mr. Oyster is on a mission to destroy time travelers  He thinks that Mr. Oyster is attempting to alter the space-time continuum  He knows he will not be allowed to do something that might impact the past  He does not believe that Mr. Oyster is offering fair compensation