20. Profile in Silver / Button, Button

A researcher from the future, a descendent of President John F. Kennedy goes back in time to witness his ancestor's death, and inadvertently changes history by saving the President. The researcher accidentally gives away the fact that he is from the future, as Kennedy is "pursued" by a series of hurricanes. A mysterious man offers a couple a bizarre deal: if they will push a button on a box that will kill one person they don't know, they will get a million dollars. After some contemplation, the couple goes ahead and pushes the button. The man tells them that they will indeed get the money. And somewhere, sometime, another couple will get the same box, and the same offer...