As Christmas approaches, Chummy and Trixie are organizing a concert. Meanwhile, Patsy takes a pair of pregnant girls to a mother-and-baby home which proves to be ill run, and Cynthia is conflicted about her future.

A new midwife arrives at Nonnatus House, and finds it hard to fit into her new role. Meanwhile, Chummy moves into the mother-and-baby home, Trixie helps a young boy in terrible need, and Sister Evangelina is in denial about her illness.

As Sister Evangelina prepares to go on sick leave, a new midwife arrives at Nonnatus House, and they immediately clash. Meanwhile, Sister Julienne encounters a face from the past, and Barbara feels under pressure.

Sister Winifred meets a young prostitute and begins a campaign to improve the lives of women like her, Trixie reconsiders her engagement when Tom is offered a post in Newcastle, and Sister Monica Joan is unexpectedly called into action.

Sister Mary Cynthia returns to Nonnatus House, Barbara has trouble communicating with a pregnant Sylheti woman, Shelagh helps Patrick with his exhausting workload, and Trixie struggles to cope with her pain.

Phyllis deals with a diabetic teenager who has fallen pregnant, Sister Mary Cynthia comes into contact with a group of Irish Travellers, and Patsy organizes a square dance to raise money for the Cubs' trip to Norfolk.

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.