The midwives receive a rapturous welcome when they return from their South African adventure - but all is not well at Nonnatus House. In their absence, Sister Ursula has been running a very tight ship and it is quickly announced that she will remain in charge at Nonnatus House, above Sister Julienne. Sister Ursula makes unpopular changes, but bound by a vow of obedience Sister Julienne is unable to challenge her. As the Nonnatuns chafe under the new rules, the midwives are drawn into helping heavily pregnant mother Trudy Watts, whose husband has just been released from prison for extortion.