 How does Conrad go back in time?
"He's dissatisfied with the current social order and killing you is part of an elaborate plan he's formulated to change it. There was no devastation, no war, no unhappiness, none of the concomitants of normal living. "And Conrad really got upset over the way Earth has been exploiting the not so intelligent life-forms on the other planets," Raymond continued. "We just come a couple of centuries or so later, that's all. We're virtually the same people ... although it is amazing what a difference two hundred odd years of progress and polish can make in a species, isn't it?" And, on those worlds, it's far cheaper to use native labor than to ship out all that expensive machinery.
 Conrad built a time transmitter using a copy of Professor Farkas' plans.
 Conrad stole Professor Farkas' time transmitter to send himself back in time.  Professor Farkas sent him back in time with the time transmitter.  Conrad built a time transmitter using a copy of Professor Farkas' plans.  Professor Farkas' assistant sent Conrad back in time using the time transmitter after Conrad gave him a bribe.