Set in London in the early 20th century, the series follows the story of three young women from very different families, who all become nannies in wealthy houses located in the prestigious Berkeley Square area in West London. For a young, respectable girl from a poor family, securing a nanny position in a wealthy home is a great stroke of luck. One of the girls, Mattie, is climbing the social ladder via the inner circle of London's finest families. Hanna is a willful young woman who ran away to London after a brief romance with the elder son of a famous Yorkshire family. Lydia is a naive and charming girl who becomes a nanny in a family with fairly modern views. Ahead of the three young women lie many adventures, tests of love and friendship. The friendship among the main characters will sustain them through good times and bad.