The Wolf and the Lion
Williams plays Arya Stark in the fifth episode of the first season of Game of Thrones, The Wolf and the Lion. While chasing a cat as part of her fencing training, she enters the dungeons of the royal castle and overhears two men plotting for the impending war between the Lannister and Stark noble families. She realizes that they are discussing assassinating her father Lord Eddard Stark, the Hand of the King, and rushes to warn him.