April 1968. Racial tensions cast a shadow over Poplar, Nancy’s eyes are opened when she supports a dying woman, and Nonnatus House welcomes a new sister.

Sister Julienne helps care for a first-time mother who is going through a challenging diagnosis. Lucille struggles with her own health, and Poplar celebrates the Whitsun Maypole.

Sister Veronica is shaken when a mother reveals a terrible truth about her marriage, Shelagh cares for a baby with a life-threatening condition, and Nancy harbours a secret.

The maternity home is thrown into chaos by an outbreak of gastroenteritis, and Nurse Crane fights to save her career. Meanwhile, Cyril encourages Reggie to seek help.

A pregnant mother with a chronic heart condition falls unwell. Nancy grows suspicious of a young father's erratic behaviour, and Matthew prepares for a visit from his father.

Trixie supports an underage mother through a difficult time, Monica Joan welcomes an unusual guest to Nonnatus House, and Sister Veronica spearheads a new council initiative

Everyone is looking forward to Trixie and Matthew's wedding and a bonny baby competition brings the community together. It's not all good news, however, as the team learn about a pregnant woman and her family living in a cramped caravan, while a worrying disease outbreak directly impacts the residents of Nonnatus House.

Nonnatus House is abuzz with excitement as the countdown to Trixie and Matthew’s wedding begins. Whilst Sister Veronica has appointed herself in charge of organising the wedding gifts, Trixie’s brother, Geoffrey Franklin, arrives from Malta and immediately starts arranging the perfect hen do. However, the approaching nuptials cause stress levels to escalate as a catalogue of small and great disasters threaten to spoil the day. Dr Turner, Shelagh and Timothy are first on the scene of a fatal car crash. Dr Turner experiences the biggest test of his career as they race against time to save a precious life. Meanwhile, Nancy considers her future, and Sister Julienne hatches a plan to save Nonnatus House once and for all.