The time-hoppers

The Time Hoppers is a science fiction novel by American writer Robert Silverberg, first published by Doubleday in 1967. The plot concerns Joe Quellen, a 25th-century bureaucrat charged with investigating "hoppers", travelers from the future whose presence in the past has been documented for hundreds of years, and his brother-in-law, Norman Pomrath, an unemployed blue collar worker who ends up being presented with an opportunity to travel back in time.