Watch the series 4 preview below:
Viewers witnessed Lady Rose and Jack Ross growing closer in last weekend's episode, when the two characters shared a romantic boat ride together.
In the first preview clip for the series finale, Lady Rose tells Mary: "I love him. And I won't listen to any imperialist nonsense about racial purity and how he should be horsewhipped for daring to dream.
"I'm going to marry him, Mary. And I don't care what it costs. And I won't keep it a secret."
Viewers are also expected to discover the conclusion to the the Anna/Bates/Green rape storyline, which has dominated the current series.
Downton Abbey's fourth series concludes on Sunday, November 10 at 9pm on ITV.