Oscar-winning actress Shirley MacLaine joins the cast of the period drama as Cora's mother Martha, who makes a grand entrance when she arrives at Downton for Matthew and Mary's wedding. However, with the couple struggling to stay united as their big day looms, will Martha's Atlantic crossing have been for nothing? Meanwhile, Mr Carson runs the rule over new footman Alfred, and Robert receives news that could leave him facing the greatest crisis of his life - and plunge the rest of the household into chaos.

Edith's big day finally arrives, but will her enthusiasm convince the family that Strallan's age doesn't matter? Meanwhile, Mrs Hughes anxiously awaits her results, Anna makes a breakthrough to help Bates, and Mary takes matters into her own hands to secure the estate's future - but the personal cost could be high.