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.

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.