As Kitty begins to unravel due to the imminent threat to her safety, Sherlock and Joan intensify their efforts to help her. Also, the origin of Sherlock and Kitty's relationship is revealed. Stuart Townsend guest stars.
It is January 1936 and diplomat Sir Hallam and Lady Agnes Holland move into 165 Eaton Place, closely followed by his widowed mother and her wayward sister. But they also need a full serving staff, for which Lady Agnes turns to an agency run by none other than Rose Buck, who used to work at the house. But the arrival of an unwelcome guest puts a strain on relations both, upstairs and downstairs.
Lady Persie's life has become increasingly complex, as she continues her illicit affair and pursues her right-wing political interests with little regard of the potential danger to those she loves. Meanwhile, Lady Agnes prepares for motherhood by having her picture taken by celebrated photographer Cecil Beaton and Sir Hallam finds himself dragged into the abdication crisis facing the monarchy.
Hank, Evan, and Paige try to help Eddie forge a relationship with Emma. Elsewhere, finding an amazing nanny helps alleviate Divya's anxiety about returning to work full-time.
