Nancy focuses on her final midwifery examinations, it is all hands on deck as the Nonnatus team prepare for what will inevitably be a busy Christmas. The maternity home is filled with expectant mums-to-be, each with their own challenging case.

1959 is drawing to a close as the residents of Poplar prepare for Christmas. Chummy and Patsy get snowed in at a failing Mother and Baby home, whilst back at Nonnatus House, Cynthia makes a momentous life changing decision.

As Christmas approaches, a bout of influenza sweeps through both Nonnatus House and the Turner family. When Mother Mildred declares that God is calling her to set up a branch house in the Outer Hebrides, it seems an ideal opportunity for the nuns and midwives to convalesce in the bracing Scottish air.

Lucille is seconded to St. Cuthbert's where she delivers a baby in an elevator; Nurse Crane gives vaccines to new students; Violet, Trixie, Sister Frances and Valerie organize a fashion show for the community.

Four new doctors arrive at Nonnatus House, causing a stir among the midwives; Fred makes a discovery while on rounds.

Sister Frances struggles to persuade the wife of a cancer patient to accept help, and as the nation obsesses over The Sound of Music, Sister Julienne considers the privileges of being a nun.