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.
Sister Julienne and Cynthia are getting donated clothing ready for charity. One parcel is set to go to St Gideon's, an institution which cares for those with disabilities and learning difficulties. Jacob, who suffers with cerebral palsy, helps Sally, who has Down's syndrome, select a pretty cardigan to wear to the institution's annual dance. Following the dance, Sally's mother discovers her feeling unwell and takes her to Nonnatus House to be looked at. The midwives find out that she is six months pregnant, which sees some difficult decisions needing to be made.
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 pays a home visit to first time mother Jeanette and the two hit it off immediately, she is also introduced to Jeannette's cousin Philip. Chummy discovers her mother has discharged herself from hospital and her illness isn't getting any better. After a falling out, PC Noakes finding Lady Browne in great distress brings her to the home to be cared for in her final days.
Jennifer prepares for Christmas at home with Philip, and reminisces about her friends and colleagues back in her youth. Rehearsals get underway for the Sunday School Christmas concert, as Chummy tries to choreograph the dancing snowflakes. Chummy is also enlisted alongside Patsy to run a poorly managed mother and baby home. Cynthia is drawn into a case which concerns two former residents of a Victorian mental hospital who have been left to fend for themselves.