Legal Question in Employment Law in Illinois

The company could sue your son to recover the money. Your son is legally obligated to pay this money back but a court, based on fairness, might rule that he shouldn't have to pay it back. Is there the possibility that the company might not have paid your son for all the hours he worked? Did he do any off-the-clock work (bring work home, respond to work emails etc)? Did he work over 40 hours per week and not get compensated overtime when he should have? This could be used to offset what they claim he owes them.