The nuns and midwives of Nonnatus House move into their new premises, and Sister Winifred, a warm-hearted, slightly innocent young woman, arrives from the Mother House. Sister Monica Joan's increasingly eccentric behavior causes concern, yet she's the one who solves a perplexing medical mystery. New housewife and mother Chummy spearheads an Open Day at the Community Centre. After helping to deliver a neighbor's baby, she decides she wants to return to midwifery.