An unforeseen event in Poplar means that Nonnatus House suffers its biggest threat yet. But this time it's not the bricks and mortar that are in danger - it's the people.

Sister Frances takes charge of a spirited young teenage mother who is shortly to move out of foster care and into her own accommodation. While Sister Frances strives to prepare her, things take a serious turn with the young mother's health.

Sister Hilda and Sister Julienne expect more from Nancy and decide to show her what she is capable of by letting her lead morning orders, and Timothy returns home from university after falling ill with glandular fever.

It is December 1967, and with Christmas fast approaching, life in Poplar is returning to normal after the terrible train crash.

The midwives move the maternity clinic into new premises and are delighted when one of their first patients through the door is Rhoda Mullocks, who the team know well. Rhoda is heavily pregnant and understandably nervous after her last baby was born with limbs affected by Thalidomide.

Nurse Crane cares for a heavily pregnant single mother, recently released from prison, while Sister Frances is called out to deliver a Sylheti mother's child in a garment factory in a rough area of Poplar.

Meanwhile, Fred decides that Poplar needs to come together to raise money for those families still affected by the train crash and pitches the wonderful idea of a festive talent show – Poplartunity Knocks!