Downton Abbey is an aristocratic estate facing a crisis. Lord Grantham's heir and his son die on the Titanic, meaning the estate will pass to a distant relative. This distant relative is Matthew Crawley, a middle-class lawyer, who arrives with his mother, Isobel. Lady Mary, Lord Grantham's eldest daughter, is expected to marry Matthew to secure the estate.

The season's central conflict revolves around the succession and the clash between the aristocratic Crawley family and the incoming Crawleys. A major turning point is the shocking death of Kemal Pamuk, a visiting diplomat, in Lady Mary's bed, creating a dangerous secret. Later, Cora suffers a tragic miscarriage, further complicating the inheritance. The season ends with the dramatic declaration that Britain is at war with Germany, fundamentally altering life at Downton.

Season 1 of Downton Abbey covers episodes 1-7. Here's everything that happened:

Season 1, Episode 1: Episode 1 - Set in April 1912, news of the Titanic's sinking reaches Downton Abbey, revealing that Lord Grantham's heir and his son perished in the disaster, creating a succession crisis. As the family grapples with the entailed estate, a new valet, John Bates, arrives, causing friction downstairs. Lady Mary's attempt to secure a marriage with the Duke of Crowborough fails. Ultimately, Matthew Crawley is identified as the new heir and invited to Downton.

Season 1, Episode 2: Episode 2 - Matthew and Isobel Crawley arrive at Crawley House, with Matthew struggling to accept his new position as heir. Isobel, a trained nurse, clashes with the Dowager Countess over hospital treatments, ultimately saving a patient's life with an unorthodox procedure and becoming chairman of the board. Meanwhile, Mr. Carson is confronted by a man from his past, Charles Grigg, but Lord Grantham intervenes to resolve the matter by paying him off. Lady Mary and Matthew's initial interactions are contentious, though a subtle connection begins to form.

Season 1, Episode 3: Episode 3 - Lady Mary is captivated by Kemal Pamuk, a visiting Turkish diplomat. After he seduces her, Kemal Pamuk dies in Lady Mary's bed from a heart attack. Mary, Anna, and Cora secretly move his body to his own room to avert scandal, but Daisy witnesses them. Meanwhile, Gwen secretly pursues a secretary career, and Mr. Bates endures a painful device to cure his limp. The episode concludes with the secret of Pamuk's death hanging over the household.

Season 1, Episode 4: Episode 4 - Lady Sybil's political activism leads her to a violent election rally, where Matthew rescues her. Mrs. Hughes reconnects with a former suitor who proposes, but she ultimately chooses to remain at Downton. Meanwhile, Cora's surprise pregnancy introduces new uncertainty regarding the estate's inheritance. Mary and Matthew share a moment, but she resists an arranged marriage, while Thomas manipulates Daisy.

Season 1, Episode 5: Episode 5 - Daisy, troubled by what she witnessed, reveals everything to Edith about Pamuk's death. Meanwhile, Sybil helps Gwen pursue a secretarial job, and Bates thwarts Thomas and O'Brien's attempt to frame him. Mrs. Patmore's failing eyesight causes kitchen mishaps. The episode concludes with Edith writing a letter to the Turkish Ambassador, exposing Mary's secret.

Season 1, Episode 6: Episode 6 - Lady Sybil's political activism at a rally leads to a scuffle, upsetting Lord Grantham. Lady Violet learns the truth about Lady Mary's indiscretion with Mr. Pamuk, creating a significant family scandal. Matthew proposes to Mary, who remains conflicted. Downstairs, Thomas and O'Brien conspire to frame Bates for theft. Bates ultimately confesses his criminal past to Carson, offering his resignation, leaving his future at Downton uncertain. Edith, meanwhile, finds a potential suitor in Sir Anthony Strallan.

Season 1, Episode 7: Episode 7 - Cora's pregnancy complicates Matthew's inheritance, and Mary delays his proposal. Misunderstanding a conversation, O'Brien causes Cora's tragic miscarriage. Anna uncovers Bates' innocent past. The episode concludes with the solemn announcement that Britain is at war with Germany, changing Downton forever.