“Empire Week” at Selfridges symbolizes all that Britain has to fight for, and it’s up to Agnes to create displays that evoke every corner of the realm. Overwhelmed, she gets unexpected help. Meanwhile, Harry gets an unexpected visit from Lord Loxley, who is suspiciously civil and offers to line up a celebrity guest for the celebration. But he wants advice from Harry in return. Mr. Crabb calls on American know-how to help Mr. Grove keep his job. Frank has a date with Kitty. Miss Mardle makes a startling revelation.