Cora makes a discovery that throws the inheritance issue into chaos, and Mary is prompted to keep Matthew waiting for an answer to his proposal. Robert arranges for Mrs Patmore to see an eye specialist, and O'Brien digs up more compromising information about Bates, but the Earl's response comes as a surprise. Thomas leaves the Abbey and Mary exacts vengeance on Edith for her treachery, while the household is rocked by a shocking announcement.