Christmas is coming, and in Poplar the midwives of Nonnatus House are busier than ever. When an abandoned baby is discovered on the steps of the convent, the whole community rallies round to provide food and clothing, and to try and trace his mother. Meanwhile, Jenny Lee finds herself drawn into the mystery surrounding elderly local woman Mrs. Jenkins, while Chummy is determined to stage an unforgettable nativity play.

Jenny celebrates her birthday with Chummy and the girls, but soon after finds herself taking care of a patient in an abusive marriage.

Chummy makes an important decision, Jenny reconnects with Jimmy, and Cynthia's conduct is called into question after the death of a baby she delivered.

Jenny is seconded to a short-staffed hospital in London, but grows increasingly reluctant to carry out her duties when she finds out she is working under intimidating surgeon Mr Tracey. Back in Poplar, the midwives are introduced to newcomer Jane and outspoken twins Meg and Mave Carter. The sisters are identical in every way, except one of them is now pregnant - forcing them to come to terms with the impact a baby will have on them.

A friend of Chummy's, Reverend Applebee-Thornton, comes to stay at Nonnatus House and soon gets on everyone's nerves. Meanwhile, Jenny and Sister Evangelina deliver a baby with spina bifida, and Sister Bernadette plays matchmaker.

Nonnatus House prepares for the annual summer fête, but when a baby show is announced, the girls must find a host for the proceedings. Meanwhile, a patient of Jenny's puts her life at risk, and Sister Bernadette remains troubled.

Doctor Turner is concerned by the spread of tuberculosis in the community, Jenny tries to repair a father and daughter's fractured relationship, and Sister Bernadette receives devastating news.

Cynthia has to administer daily insulin injections to diabetic John Lacey, a bully who consistently belittles his wife Annie. When Annie’s beloved son Bob pays a visit, Annie gains the confidence to start to turn her life around. Jenny looks after a black mother to be, Monique, who is subjected to racial prejudice from her neighbours.

The convent comes under threat of demolition. Fred's pregnant daughter and her young son come and stay with him. Jenny is wooed by a new love interest. Chummy and PC Noakes prepare for the arrival of their baby.

An unexploded bomb is discovered in Poplar, throwing festivities into chaos.

After the closure of Nonnatus House, the nuns and midwives finally move into their new premises. Sister Winifred arrives from the Mother House. Jenny is worried about new mother Merle’s mental state and the welfare of her baby who isn't feeding properly. Dr Turner is worried that it could be something more serious.

Trixie's feathers are ruffled when Jenny is promoted, but the new Acting Sister has more to worry about after a mother-to-be reveals the baby she is carrying doesn't belong to her husband - and to complicate matters, the real father is black. Cynthia is inspired by a lecture on natural childbirth, convinced it will help an overly anxious patient, while Alec and his friends try to persuade Jenny to join them on a CND march.

Sister Julienne receives an SOS from Holloway Prison, whose usual maternity workers have been struck down by illness, and when she and Trixie step in to help, the nun puts her reputation on the line to prevent a heavily pregnant convict having her unborn baby taken away by social services. Shelagh faces heartache when a routine pregnancy check reveals something far more serious, Alec has a confession for Jenny and Fred takes the gang to the theatre to celebrate Chummy's birthday - only for the trip to end in disaster.

Jenny has an eventful few days, starting with a patient who as well as having herself to worry about, is also struggling to cope with her mother, an agoraphobic who hasn't been outside for at least 12 years. On top of that, Alec asks the midwife to accompany him to Brighton for the weekend, leaving her wondering if his intentions are strictly honourable. However, things soon take a tragic turn. Meanwhile, Shelagh joins the local choir to take her mind off her problems.

The nuns and midwives are busy preparing for Sister Evangelina's surprise jubilee celebrations, marking 50 years since she took her vows, but a face from the past threatens to ruin the party for the guest of honour. It's back to business when a young woman with Down's syndrome is brought in feeling unwell. To everyone's surprise, they discover she is six months pregnant, causing some of them to think the worst, and the staff are joined by new nurse Patsy, whose sense of humour and no-nonsense attitude make her an instant hit.

Tom, the local curate, asks Trixie to join him for a day of cricket. She accepts, but the date is disastrous. Shelagh decides to talk to Dr. Turner about adopting a baby. Patsy, struggling to adapt to the unpredictable and chaotic life that midwifery brings, upsets a young mother in the clinic.

Sister Julienne calms an anxious new mother who has put her baby in danger. Jenny, seconded to The London, is impressed with the facilities, but soon begins to see cracks in the establishment. Chummy is upset to learn that her mother has walked out on her father, leaving Lady Browne penniless. As Dr. Turner and Shelagh continue the adoption process, they uncover a devastating secret.

Jenny is assigned to first-time mother Jeanette, who requires frequent visits during a protracted labour, and when she meets her patient's cousin, Philip, a new friendship begins to grow for the midwife. Meanwhile, Chummy worries about her mother's illness when she discovers Lady Browne has discharged herself from hospital.

When harsh conditions at a home for unmarried expectant mothers are exposed, Chummy and Patsy are required to take over the running of the home, and later help a young mother decide that she is not as set on giving her baby up for adoption as she had thought. Cynthia wrestles with a calling to become a nun, but an encounter with a former mental hospital inmate helps her to make up her mind and she leaves midwifery behind to become a postulant.

A chance encounter with an impoverished child forces Trixie to see an unfamiliar darker side of life. As Nonnatus House welcomes a new resident, Nurse Barbara Gilbert, Tom Hereward has a surprise romantic gesture in store for Trixie.

Trixie and Sister Mary Cynthia help a deaf-and-dumb woman, and Barbara has a baffling case. Meanwhile, Fred's daughter arrives from Birmingham and interferes with his and Violet's engagement, and Delia has a proposal for Patsy.