After the death of the heir, Violet wishes that Robert's daughter Mary could inherit Downton Abbey.
Matthew Crawley and his mother Isobel arrive at Downton, and have difficulty settling in. Carson is mortified when confronted by his past. Violet attempts to promote a match between Matthew and Mary. Isobel is elected to serve on the hospital board.
Cora's tries to set up Mary with Evelyn Napier, who falls for his friend instead, with significant consequences for the household. Bates takes action to help cure his limp.
Mrs Hughes finds herself the focus of speculation when she meets a former suitor who makes her question her position. Violet and Isobel clash over a medical ailment affecting Molesley. Carson is concerned there is a thief at work in the grounds.
Isobel finds herself at odds with Violet. Mary is introduced to a potential suitor but wants to be with Matthew. Anna works out who stole a valuable snuff box. O'Brien plans a way for Edith to get even with Mary.
Sybil puts herself in danger when a fight breaks out. Sybil's sisters notice Matthew's feelings for her. Mary is surprised by a marriage proposal. Bates clears his name over the missing wine but resigns rather than name the real culprit.