Gebardi (defendant), an unmarried man, and a single woman agreed to travel from state to state by train and engage in sexual intercourse. Both were indicted for conspiring to violate the Mann Act which made it a felony to conspire with others to transport an unmarried woman from one state to another for the purpose of engaging in sexual intercourse. At a trial without a jury, there was no evidence supporting the allegation that any other person had conspired. The trial court found Gebardi and the woman guilty and their convictions were affirmed by the court of appeals. The U.S. Supreme Court granted certiorari to review the judgments of conviction.