 Why is Simon so unenthusiastic when the client shows up at the beginning of the story?
"Providence," Simon told her whilst fiddling with the aspirin bottle, "will provide." The client fussed himself with Betty's assistance into the seat, bug-eyed Simon, said finally, "You know my name, that's pretty good. 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. 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.
 He knows he cannot accomplish what Mr. Oyster is asking, and knows he will have to turn him away.
 He knows Mr. Oyster's reputation, and does not want to get involved in his affairs.  He knows he cannot accomplish what Mr. Oyster is asking, and knows he will have to turn him away.  He only takes on easy cases that he knows will pay the bills.  He has too much of a headache to deal with the new client.