The last episode of season four of "Downton Abbey" featured Rose's glamorous ball, a visit from friends across the pond and Lady Edith's big decision. 

On the season finale, the group goes to London to partake in the festivities surrounding Lady Rose's (Lily James) debutante's ball. The actual ceremony consists of Rose curtsying before the King and Queen of England, in addition to the Prince of Wales. The presentation goes off without a hitch, but the real drama takes place outside of the main event, both upstairs and downstairs. 

Most of the downstairs staff goes to London, where they meet some Americans who are assisting Mrs. Levinson (Shirley MacLaine) and her son, Mr. Harold Levinson (Paul Giamatti), who have come over from America to go to Rose's coming-out ball. 

In London, Daisy (Sophie McShera) meets Mr. Levinson's servant, whose casual, upbeat American manner is a bit jarring to the traditional, reticent British help. The American servant takes a shine to Daisy, and gives her an offer, per Mr. Levinson's request, to come to America to cook for for his employer. 

Mr. Levinson, who is not too comfortable with the staid ways of the British upper class, begins to form a relationship with one of Rose's friends, Madeline, who was also recently presented. 

Back at Downton, Thomas Barrow (Rob James-Collier) is forced to be the footman to Branson (Allen Leech), who traveled to London a couple days after the rest of the family left. Barrow, who is already not happy about being a footman to the former chauffeur, sees Branson upstairs, at night, with Sarah Bunting (Daisy Lewis). While Branson was only showing Ms. Bunting the estate, Barrow suspects otherwise, and takes the opportunity to tell Lord Grantham (Hugh Bonneville) the development once they're down in London. 

In London, Mrs. Hughes (Phyllis Logan) is orchestrating a coat drive to donate old coats to refugees. Anna (Joanne Froggatt) gives Mrs. Hughes one of Bates' (Brendan Coyle) old coats, in which Mrs. Hughes finds an old train ticket that reveals Bates did go to London on the day Mr. Green was found dead in Piccadilly. 

Meanwhile, unscrupulous card shark Mr. Sampson arrives at their London residence with Lady Rosamund (Samantha Bond). While at a club after dinner, Sampson steals the contents out of a purse from one of the ladies in attendance. The purse belongs to a woman who is having a fling with the Prince of Wales, which would create a huge monarchial scandal if released to the media. The woman discovers that a love letter written to her from the Prince is missing from her purse, and immediately fingers Sampson as the culprit. 

Lady Mary (Michelle Dockery), Rose and Charles Blake (Julian Ovenden) go to Sampson's apartment to look for the letter, but it is nowhere to be found.

Later, when Sampson is leaving the Crawley's after a game of poker, Bates finds the letter in his suit jacket, and gives it to Lord Grantham. 

Mary, who was contemplating turning Bates in to the authorities for most likely murdering Mr. Green—even though Green was an odious man—decides against it in repayment for Bates' undying loyalty to the Crawley family. 

At Rose's ball, everyone is shocked to see the Prince of Wales make an appearance to have the first dance with Rose. 

Downstairs, Mr. Molesley (Kevin Doyle) tells Mrs. Baxter (Raquel Cassidy) to stop being swayed by Barrow, and hints at his romantic interest in her.  

Up at the party, Lord Gillingham (Tom Cullen) tells Mary the truth about Charles Blake: he's also an aristocrat. Mary decides that she is ready to have a romantic life again, and will let her two suitors battle it out to win her heart. 

Edith (Laura Carmichael), who is devastated after having to give up her daughter to a family in Switzerland, decides to take matters into her own hands and make plans to bring the child back to live with a tenant farmer at Downton. 

In the end, the downstairs staff go to the seaside for a day of relaxation after orchestrating the ball.

At the shore, Daisy turns down the American servant's request to cook for Mr. Levinson, and he reveals that he asked her specifically because he likes her romantically. Daisy turns him down, so Ivy (Cara Theobold), who is itching to get out of Downton, tells him that she'll go to America to cook for Mr. Levinson in her stead. 

The end of the season raises an array of questions: Did Bates kill Mr. Green? Who will Mary choose? What will happen once Edith brings her child to Downton? 

Alas, fans won't find out until next year, when "Downton Abbey" resumes for season five.