Tortured countineously to resign and then released in one day against service contract of 90 days notice

My brother was tortured verbally by boss on several occasions and ultimately he got frustrated and resigned stating to be released as per terms of contract. He attached resignation letter through a email and he wrote in email the stress creating reasons and also that because of this he decided to resign But his company released him on the same day whereas notice period of 90 is there as per employment terms. Can he legally file a case against company for re-employment or release as per terms of contract