 Why does Mr. Oyster want to hire Simon and Betty?
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." Simon seemed incapable of carrying the ball this morning, so Betty said, "But ... Mr. Oyster, if the future has developed time travel why don't we ever meet such travelers?" Mr. Oyster returned his glasses to their perch, bug-eyed Simon, but then nodded. 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.
 He thinks the time traveler will have the secret to never-ending youth.
 He thinks the time traveler will have the secret to never-ending youth.  He wants to know the secret of time travel and they are the best investigators around.  He wants to make sure his family's wealth continues in the future.  He wants to find out a secret for political reasons.