A chance encounter with an impoverished child forces Trixie to see an unfamiliar darker side of life. As Nonnatus House welcomes a new resident, Nurse Barbara Gilbert, Tom Hereward has a surprise romantic gesture in store for Trixie.

Barbara faces her most challenging case to date when she treats first-time mother Abigail Bissette and the birth does not go according to plan. As Sister Julienne struggles with the increasing financial pressure on Nonnatus House, a mystery benefactor comes to the rescue. Elsewhere Sister Evangelina is unimpressed by newly arrived nurse Phyllis Crane.

The Nonnatus team rallies to support first-time parents Marie and Tony Amos when Tony is arrested for gross indecency with another male. Elsewhere, as Poplar is gripped by an outbreak of dysentery, Trixie undertakes her first official church duty since her engagement to Tom.

The midwives face one of their busiest nights to date, whilst Sister Winifred concentrates her efforts on the prostitutes of Poplar. Elsewhere, cracks start to appear in Trixie and Tom Hereward's relationship.

Sister Julienne's faith is challenged when a mother refuses medicine for her newborn baby. Dr Turner's involvement in the case forces him to face his own demons. Meanwhile, Barbara must work out a way to communicate with a pregnant Sylheti woman.

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.