 Why did Opal let Rog go back to Earth?
Eudalia had been a female foreman in a garment-cutting shop before being captured and brought through. It arrived before the meal, materializing against one of the seven walls of the roofless chamber. "They pass through their gateway to Earth at considerable danger and, probably, expense of some kind. He had felt the inner tug of command, said good-by to the women and returned to his smaller compound within its own barrier dome. As in all of this strange universe, excepting the dome-cages in which the captives were held, the training hall followed no rules of three-dimensional space.
 because the aliens weren't good at capturing other men
 so he would fall out of love with his wife  so he could try to escape and fail  because the aliens weren't good at capturing other men  as a reward for his hard work