Boxing Day sees heavy snowfall covering the country and the adverse weather causes major disruption across Poplar as roads become blocked and pipes freeze meaning families have to queue outside for water from standpipes. Sister Julienne must inform a family about the death of their loved one and uncovers an uncomfortable truth, while Valerie helps an unmarried couple living in a caravan prepare for their baby, but unforeseen complications knock her confidence in her ability as a midwife. Guest starring Anita Dobson.

The winter continues, and the team at Nonnatus House welcome their newest midwife, Lucille Anderson. Nurse Crane and Dr Turner care for an elderly cancer patient facing eviction.

Lucille faces racism and prejudice when a new mother falls ill. Sister Winifred is keen to have fathers be more involved in the care of their babies.

A pregnant mother hears a devastating diagnosis. Fred and Violet organise a beauty contest. Trixie and Christopher's relationship feels the strain.

Sister Julienne is drawn into the heart of a different culture when she is called upon to help a Pakistani family. Having come to terms with her own childlessness, Mumtaz Gani is heartbroken when her husband Saddiq brings home a second wife who is eight months pregnant. Sister Julienne must help Mumtaz come to terms with this new addition to her family.

Lucille must win the trust of a mother who is terrified of giving birth. Nurse Crane and Dr Turner are anxious to find a possible smallpox sufferer.

Barbara gets involved with a recently widowed pregnant woman, and Sister Monica Joan has her cataract surgery.

Dr Turner gets involved with a troubled young man, and Lucille makes new friends. Meanwhile, Barbara lies ill in hospital.

The team must rally to prepare for Sister Monica Joan's birthday. Meanwhile, the closing of a nearby maternity home brings an influx of expectant mothers to the Nonnatus midwives.