Which wife should a husband return to after his travels if he departed from one of them and returned on the same day, knowing that he usually stays overnight with the second wife on normal days?

If the traveling husband returns, he should spend the night with the wife whose turn is next, and not complete the turn of the first wife. Al-Shafi'i said in Al-Umm: "If he had allotted a turn for a woman, then absented himself, then returned, he should begin the allotment with the one whose turn comes next. And similarly, if he was present but preoccupied from spending the night with her, he should begin the allotment just as a person returning from absence begins it, by starting the allotment with the one whose night it was."