 How does Conrad go back in time?
Conrad's idea had been to go back in time and "eliminate!" In that way, there would be no space-drive, and, hence, the Terrestrials would never get to the other planets and oppress the local aborigines. "I wormed the whole thing out of him and all of us—the other cousins and me—held a council of war, as it were, and we decided it was our moral duty to go back in time ourselves and protect you." "Well, five years is rather a long stretch for any girl to spend in exile," Raymond explained, "even though our life spans are a bit longer than yours.
 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.