The nuns are a group of dedicated and compassionate women who live together at Nonnatus House, an Anglican convent. They're led by Sister Julienne, the wise and pious Sister-in-Charge.
Despite their age and wisdom, they're not all perfect. This is reflected in their personalities: Sister Monica Joan, who has a bad memory, enjoys astrology, knitting, and arcane mysteries; Sister Evangelina, who is skilled and compassionate; and Sister Bernadette, who identifies with the younger nurses.
They're also funny and endearing. In Series 6 for example, everyone is upset when strict Sister Ursula gives away their television set. But when Nurse Crane asks why, Sister Monica Joan explains that she is lonely because nobody really talks to her.
She also demonstrates her love of literature when she quotes Keats at opportune times. This is a rare and beautiful expression of a true bibliophile that makes us catch our breath.
Another great quote is when Sister Evangelina and Nurse Crane start to argue about their own lengthy careers as nurses and midwives, Sister Monica Joan rises to the challenge with forceful logic that proves she is not only a highly competent nurse but also a much better choice of representative for this particular group of nuns.
She also manages to bring a little magic into the season when she persuades her fellow nuns to allow her to go home for Christmas. The other nuns don't understand why she doesn't just stay put, but she gets to return to Poplar at Christmastime and be amongst her loved ones – and it all goes down well.