It’s 1958 and Nurse Jenny Lee discovers the Nonnatus House community gathered to wish her a happy birthday as she returns from work. Chummy, Trixie and Cynthia then go to the cinema with her. Her good cheer is soon short lived though the next day when she is assigned a new patient called Molly Brignall. Trixie and Sister Evangelina end up in the middle of some unusual circumstances, aboard a Swedish cargo ship when they look after the captain’s daughter, who is about to give birth for the first time.

The unexplained death of a newborn baby delivered by Cynthia puts the midwife under intense scrutiny from the police and the pregnant women of Poplar, placing immense strain on her work and health as she questions her own abilities. Chummy faces pressure of a different kind as she and PC Noakes pursue a dream which could bring exciting changes for the couple, while a chance encounter returns Jimmy to Jenny's life - with surprising results.

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.

Jenny returns from her stint at the London Hospital and heads straight into one of the most emotive cases of her career when she and Sister Evangelina assist at the birth of a baby with spina bifida. As the parents struggle to come to terms with their son's life-limiting condition, Jenny, who has never delivered a disabled child, also fails to comprehend the far-reaching implications for the family. Meanwhile, Nonnatus House plays host to an acquaintance of Chummy - the Rev Applebee Thornton, an eccentric cleric who befriends Jane.

The locals excitedly prepare for the summer fete, featuring a baby show for which Trixie volunteers to secure a celebrity judge. Not everyone is in the mood for a party, however, as Jenny finds when she meets Nora Harding, a mother-of-eight distraught that she will soon have another mouth to feed. The midwife does her best to reassure the desperate mum, but her words fall on deaf ears and Nora ends up taking matters into her own hands.

Crowded living conditions mean that tuberculosis has been rife in Poplar. A mass-Xray programme to diagnose the disease early though is introduced and Dr Turner is determined that the community will no longer live under the threat of the disease. The nuns and nurses attempt to support the doctor in his campaign to bring proper screening facilities to the area and Jenny’s district nursing rounds lead her to a family who have suffered devastating misfortune from the disease.

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.

Chummy and Peter prepare to become parents, while Sister Bernadette faces her own crossroads. Jenny attracts a new admirer.