September 1938: Chancellor Hitler of Germany has sparked an international crisis over his government’s claims to parts of Czechoslovakia. In hopes of averting war, British Prime Minister Chamberlain negotiates with the Nazi leader through the British Foreign Office, headed by Lord Halifax. But Halifax’s private secretary, Sir Hallam Holland, is dead set against the official policy of appeasement.
Against this backdrop, Hallam’s new baby daughter arrives home at 165 Eaton Place with her exhausted mother, Lady Agnes. Much has changed since the last season of Upstairs Downstairs: Hallam’s mother, Maud, has died and her ashes are ensconced in an urn on the mantelpiece; Hallam’s aunt, Dr. Blanche Mottershead, is staying over after Maud’s funeral in a ill-advised effort to make herself useful; Rose, the head housekeeper, has been diagnosed with tuberculosis and is recovering at a sanatorium; and Beryl, an attractive nursery maid, has just been hired.
Beryl is a welcome distraction to Harry, the chauffeur, who has returned to his senses after a failed romance last season with Lady Persie, Agnes’s rebellious little sister. Persie is now burning her candle at both ends with various Nazi lovers in Munich.
Ever the meticulous man in charge, Mr. Prtichard, the butler, has volunteered to help with war preparations and is supervising distribution of gas masks to the neighborhood. He even acquires a gas-proof pram for the new baby. Trying to do his part, Johnny, the footman, tests the pram by putting Maud’s pet monkey into it next to the tailpipe of Hallam’s car, while it is running. Unfortunately, the monkey asphyxiates.
Since Johnny already has a strike or two against him, Pritchard takes the blame when a police sergeant shows up, bent on enforcing the law against mistreating animals. At the police station, Pritchard’s previous record comes out: during World War I he was jailed as a conscientious objector, something unknown at Eaton Place. The news strikes a nerve, rekindling bitter memories for Mrs. Thackeray, the cook, who lost her husband in the war, and Mr. Amanjit, Maud’s private secretary, who was wounded at the Second Battle of Ypres.
Tempers cool when Agnes reminds everyone that they are on the same side—underscored by Hallam’s sudden trip to Germany to help Chamberlain negotiate with Hitler. While there, Hallam chances on Persie at a night spot. He warns her that war is inevitable and offers to take her back to England. But she demurs, giving him an unexpectedly soulful goodbye kiss.
The episode ends with Chamberlain’s arrival back in England. Standing on the tarmac next to a British Airways Electra, with a very glum Hallam in the background, the prime minister triumphantly announces an agreement with Hitler “never to go to war with one another again.”