O'Brien tries to stir up trouble for Bates by writing to Mrs. Bates, but when she realizes that Mrs. Bates is threatening to ruin Mary and her family's reputation, she switches sides. O'Brien may not like Bates, but some things are more important.
Thomas cares about William when he's dying and is annoyed he can't be transfered to Downton, because their hospital is for officers only. But the Dowager Countess steps in, gets Thomas transferred, and talks the minister into allowing William to be married to Daisy on his deathbed. Maggie Smithh is seriously amazing.
Branson and Sibyl come close to something. The war is making that invisible boundary that separates them disappear... sort of. Mary is forced to tell Sir Richard about her scandalous past and he thinks the fact that she has taken a lover puts them on more equal footing (it totally doesn't... I love Mary).
In things that annoyed me, Edith continues to be a good person, which feels out of character. I never saw her change and I still don't like her. The pregnant housemaid, Ethel, has a baby and the officer/father wants nothing to do with her. She's poor and barely scraping by. I hate her character and this story line.
Then, because I can't talk about this episode without talking about it... Matthew loses the use of his legs and his ability to, erm, produce an heir. He tells Lavinia to leave him. He believes he can not marry any woman. This creates some serious drama. I love Matthew!