Dinosaur hunter Reggie Rivers and his partner, the Raja, organize time-travel safaris in a
world with a Hawking-style chronological protection principle.
Oh, I’m no four-dimensional thinker; but, as I understand it, if people could go back
to a more recent time, their actions would affect our own history, which would be a
paradox or contradiction of facts. Can’t have that in a well-run universe, you know.