Major "Patrick Gordon", a member of the Princess Patricia's Canadian Light Infantry, made a request to stay at the convalescent home at the Downton Abbey in 1918 because he claims to be related to the Crawley family. The soldier has a Canadian accent and major burns and injuries on his face (which is largely covered in bandages).
Gordon meets Edith. Edith mentions to him that they haven't found the family connection yet, though there was an aunt who married a Gordon. Gordon tells her that is not the connection, then asks her if she recognizes him. He claims they met a long time ago.
Later, Gordon tells Edith he came to Downton frequently while growing up. Suddenly she realizes who he is claiming to be, and tries to ask him but cannot get the words out. Major Gordon then responders to question that yes, he is Patrick Crawley. He claims that he survived the Titanic sinking, but developed amnesia and was sent to Canada since he was mistaken for a Canadian. He did not correct them because he had no memory of who he really was. Instead he remained in Canada, taking his surname from a bottle of Gordon's gin. It was only after the fighting that he suddenly regained his memory.
While in hospital recuperating, he tells Edith that he verbally told the doctors and nurses there what he could remember about his time on Titanic and they wrote down his account. It is impossible to recognize Major Gordon or compare a handwriting sample as his face was severely burned and his hand was amputated during the Battle of Passchendaele.
Gordon does convince Edith by relating vague experiences in Downton and telling her that Patrick loved her the whole time, tears running down his eyes. Mary however is immediately convinced the officer is lying. Lady Mary refuses to visit him, and the rest of the Crawleys refuse to meet him also. Robert Crawley hesitantly visits him. Robert does not believe he is Patrick Crawley, until he rubs his mouth in a peculiar way. Robert is about to leave the room, but stops, recognizing that Patrick Crawley used to wipe his lips in the same fashion. Robert is stunned and asks, "where did you learn how to do that?" Patrick claims not to know what he means.
Lord Grantham sends Major Gordon's story to his solictior who does some investigating. He reveals that a Peter Gordon once worked with the real Patrick Crawley at the Foreign Office, which would explain how he knew some of the private details of the Earl's family and Patrick's strange mannerism of wiping his lips with his fingers. Violet is then convinced Major Gordon is a fake, most likely Peter. Major Gordon tells Edith he and Peter were good friends. Edith says Murray will then try to track down Peter, to which Major Gordon nervously questions what if he had joined his regiment.
Frustrated that no one else recognizes him as Patrick, Major Gordon tells Edith that there may be no going back, but Edith encourages him not to give up. Patrick, upset that Robert does not acknowledge him as Patrick Crawley or possibly unwilling to wait and be exposed as a fraud, decides to leave without saying "goodbye" in person to Edith. He leaves a letter for Edith, signing it "P. Gordon." Sybil questions whether P stands for Patrick or Peter. In the end, Edith holds the letter from him, and struggles with her emotions about whether he was really Patrick Crawley or if the whole thing was a cruel fraud.