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.