Full of old-line rectitude Lady Mary suspects Mr. Bates murdered Mr. Green. The reason was raping Anna. Mary feels she has to do the right thing and trun in Mr. Bates. That's even though Anna is her "groomer." Then Mary seems to back off from all that. Mr. Bates' criminal mindset and skills turn out to be useful in London.
So, we fans of "Downton Abbey" wonder if Mr. Bates will get away with murder. By next season that will be a very small issue. The world will be in upheaval. Edith alluded to the Brown Shirts. The Great Depression and then World War II are coming. Also in upheaval is the financial condition of the family. Is Thomas mature enough to guide Robert into putting profit above tradition and paternalism? Mary is between two worlds. She may not be enough in the real one to save the mansion.