As time goes by, Downton Abbey still maintains its superficial calm and unchanged appearance. After his successful proposal on Christmas Eve, cousin Matthew (Dan Stevens) begins planning his wedding with Mary (Michelle Dockery). Edith (Laura Carmichael) is still fighting for her own happiness. Pregnant Sybil (Jessica Brown-Findlay) returns to Downton with her driver Brandon (Allen Leech) to prepare for Mary's wedding. Downton Abbey, which seems to be going smoothly, also has disturbing factors lurking. The master (Hugh Bonneville) is informed that the investment failed and Downton Abbey may not have the funds to maintain it. On the other hand, Matthew becomes the candidate to inherit the estate of his ex-fiancee Lavinia's father. The two people ahead of him have lost the conditions for inheritance for various reasons. Matthew unexpectedly obtains a huge fortune, but he is not prepared to accept it due to his uneasy conscience. Bates is still in prison, waiting for the day to come out. Around the word "change", the transformation of Downton Abbey is inevitable...