A pair of school friends are unexpectedly reunited in the delivery room, and a mix up results in complications for both. Meanwhile, Barbara helps a couple in need of assistance, and Patsy's secret relationship with Delia pains them both.

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.

The introduction of the contraceptive pill is welcomed by Dr Turner, but some of his colleagues are less keen on the idea. Patsy tries to help a bargee who wants to give birth among her own community rather than in a maternity ward. Nurse Crane deals with an emergency during a storm, and a familiar face returns to Nonnatus House - but has been changed by her time away.

Dr Turner is horrified to realise he may be partly to blame as the cause of the recent rise in birth deformities comes to light, and tries to prevent further cases. Sister Evangelina returns to work, but has clearly been affected badly by her stroke, and her health continues to deteriorate. A pregnant bride goes into labour during her wedding reception, while her mother is forced to come to terms with her grandchild being conceived out of wedlock.