Once considered the vulgar venture of an upstart American, Selfridge & Co. is now the toast of London, about to celebrate its fifth anniversary. The store's staff plans a surprise for Harry, and unexpected guests show up. Meanwhile, the latest sensation is a new nightclub, run by libertine Delphine Day, who is a new friend of Harry's wife, Rose. Are the two institutions—Selfridges and Delphine's—destined to cross paths? In other action, Lady Mae's husband, Lord Loxley, is back in her life again. Rose spots a ghostly but familiar face at Delphine's. And Agnes gets a huge promotion but makes a bitter enemy. On the larger stage, the Archduke of Austria is assassinated, touching off a crisis on the Continent.

It's August 1914, and Britain is now at war with Germany. Expecting the great adventure to be over by Christmas, young men flock to enlist, including a large contingent of Selfridges staff. Though an American himself, Harry rises to the occasion, promising the men their jobs when they return and hosting a benefit for victims of the German invasion of Belgium. Mr. Grove shocks Mr. Crabb with a bold strategy for meeting the store's manpower needs. Lord Loxley's plot deepens. And Henri gets deeper into a mysterious transaction.