It’s November 1970 and the countdown to Nancy (Megan Cusack) and Roger’s wedding is on. Reggie (Daniel Laurie) has made a vase for a wedding gift, but when he is chased by a group of teenage boys and falls, the vase is smashed.
When a Mother and Baby Home is evacuated due to a fire, a handful of mothers return to Nonnatus House, including 14-year-old Paula Cunningham who is almost at term. Paula is initially admitted to the maternity home for a urine infection, but being on the ward is too upsetting and Dr Turner (Stephen McGann) transfers her to the Mother House near Chichester.
Cyril (Zephryn Taitte) oversees Paula’s welfare as her social worker, whilst the Nonnatus team support her through a traumatic delivery. Elsewhere, Paula’s parents Grace and Philip Cunningham choose to wait at home but the situation is taking its toll on them too.
At the Mother House, a familiar face is there to greet the visitors. Sister Hilda (Fenella Woolgar) welcomes Sister Catherine (Molly Vevers) and Sister Julienne (Jenny Agutter) who have escorted Paula.
Sister Catherine feels blessed that her sister, Helen Cantwell, is attending her First Vows ceremony. When the two sisters are reunited on the beach close to the Mother House, Sister Catherine is even more ready to join the Order, and Sister Veronica (Rebecca Gethings), Sister Monica Joan (Judy Parfitt), Sister Hilda and Helen all attend Sister Catherine's First Vows.
Meanwhile, Colette and Nancy stay with Miss Higgins (Georgie Glen) ahead of her wedding to Roger (Conor O’Donnell). During a final dress fitting with Violet (Annabelle Apsion), Miss Higgins and Nurse Crane (Linda Bassett), Nancy shares some surprising news.
Shelagh (Laura Main) hosts a hen-party assisted by Geoffrey (Christopher Harper) but the following morning Nancy is feeling unwell and Nurse Crane’s help is summoned.