An unexploded bomb is discovered in Poplar, throwing festivities into chaos.

When harsh conditions at a home for unmarried expectant mothers are exposed, Chummy and Patsy are required to take over the running of the home, and later help a young mother decide that she is not as set on giving her baby up for adoption as she had thought. Cynthia wrestles with a calling to become a nun, but an encounter with a former mental hospital inmate helps her to make up her mind and she leaves midwifery behind to become a postulant.

Festive cheer is in plentiful supply as Poplar readies itself for Christmas. An unexpected surprise for a grieving mother helps bring the Christmas magic home, while Nonnatus is rocked to the core when one of its own goes missing.

The nuns are trying to help a tiny struggling mission hospital on the Eastern Cape. But can they save the hospital from closing down – and perform a Christmas miracle a long way from home?

Boxing Day sees heavy snowfall covering the country and the adverse weather causes major disruption across Poplar as roads become blocked and pipes freeze meaning families have to queue outside for water from standpipes. Sister Julienne must inform a family about the death of their loved one and uncovers an uncomfortable truth, while Valerie helps an unmarried couple living in a caravan prepare for their baby, but unforeseen complications knock her confidence in her ability as a midwife. Guest starring Anita Dobson.

As Poplar prepares for Christmas, the nuns leave for the Mother House to vote in a new mother superior and to help care for a group of Chinese orphans. Meanwhile, Trixie returns to Poplar refreshed and is shocked to discover that many mothers no longer want to give birth at home.

Mother Mildred and the Nonnatus House team head to the Outer Hebrides in response to a nursing shortage.

The circus comes to Poplar, putting a magical spell on its residents. A delighted Shelagh is reacquainted with an old friend, and Trixie receives an unusual gift.

Christmas promises to be a memorable one at Nonnatus House as Lucille and Cyril prepare for their upcoming winter wedding. The Nonnatus team are faced with their busiest Christmas Day ever as the Maternity Home is filled with expectant mums-to-be, each with their own challenging case. Luckily Mother Mildred is on hand to support the team.

The Turners support a family still suffering the devastating effects of thalidomide, Miss Higgins is involved in an unexpected delivery, and the community stages a talent show.

As Poplar prepares for Christmas, Sister Monica Joan fears this could be her last. Dr Turner and the midwives deal with a complicated multiple birth, and Cyril helps a war veteran.