Margaret Merchant (Claire Foy) is the villainess from "The War in Words," a sketch from the December 1, 2018 episode of Saturday Night Live. She is the wife of James Merchant, a British soldier serving in World War I.
The sketch featured James writing to Margaret from France to their home in Brighton, England, with Margaret responding to his first two letters with very short messages. Frustrated, James asked Margaret for a photo of herself in her next reply, only for Margaret to send James a photo of herself as a child, and also assuming that James and the other soldiers would be aroused by the picture. When James asks for a more current photo, Margaret sends one of herself with a man named Henry, prompting James to wonder if Margaret is having an affair.
Henry responds to James' latest letter with a reveal that Margaret was in trouble with the law, but it was never revealed what crime she committed. James sent a letter asking who exactly Henry was, only for Margaret to vaguely respond that Henry was the man in the photograph with her, while asking James to wish her luck on the trail and also asking how WWI was going, leaving James bewildered that she would call it "World War I."
The sketch ended with Margaret responding to James' last letter by promising to explain everything to him when she sees him in France, revealing that she has joined the army. While donning a military uniform, Margaret revealed that she will serve as a gunnery maid...for the German army (the German Empire being precursors to the Nazis at that time). After completing her letter, the evil Margaret put on a German army helmet, cementing herself as a traitor and villainess, leaving James shocked that his wife was fighting for the enemy.