Having dealt with some extremely naughty sheep last year in the Outer Hebrides, this year the gang are in Poplar. Everyone is hoping for a nice uneventful Christmas, but of course that doesn't happen! Sister Monica Joan is rushed to hospital, while Trixie is less than impressed to receive a subscription to a Marriage Bureau as a Christmas present. Meanwhile, the circus is in town as ex Time Lord Peter Davison plays Mr Percival the Ringmaster.
Dr Turner and Nurse Crane must deal with an alarming outbreak of diphtheria. Fred finds an abandoned baby in a dustbin, and the team must help locate its mother.
Sister Julienne cares for a pregnant prostitute, while Dr Turner puzzles over a mysterious string of symptoms.
Lucille is seconded to St Cuthbert's when a ward sister is off sick, but a lift malfunction sees her spend the evening with mother-to- be Connie instead of her planned rendezvous with Cyril. Nurse Crane tries to help a woman who is newly arrived from East Pakistan, while Shelagh enlists Violet, Trixie, Sister Frances and Valerie to put on a charity fashion show to raise money for the incubator fund.
Sister Julienne volunteers to put up four trainee doctors at Nonnatus House while they undertake the practical aspect of their obstetrics diploma, hoping the exercise will remind the council how vital the home is to the community and help remove the threat of demolition. There is a lot of excitement about the new arrivals and the doctors don't disappoint. On his CDC rounds, Fred comes across a street marked for demolition, with one house clearly showing signs of life.
Sister Frances is at a loss when she cares for diabetic and recovering cancer patient Albert Calthorpe whose fiercely independent wife Grace refuses to accept further help, despite caring for her husband, her elderly mother and her pregnant daughter. Meanwhile, Violet is given two tickets to new hit film The Sound of Music and decides to raffle them off with all proceeds going to the incubator fund, while Timothy, Angela and May want to give their parents a night off, but they're not sure how.
At the Turners, Shelagh receives a phone call from the Hong Kong adoption agency, which has the alarming news that someone from May's past has arrived in the UK and wants to see the little girl. Meanwhile, Valerie's cousin Maureen is heavily pregnant and hoping her baby will be born on Thursday, the same date as her father and grandfather. However, her due date isn't so soon and keen to bring on the birth, Maureen takes a big risk by secretly taking castor oil - with potentially disastrous consequences.
Trixie helps a blind mother, Marion, care for her new baby, but trouble starts when Marion's sister calls Social Services to intervene.
Sister Julienne decides it is time to take matters in hand when a letter arrives from the council saying that it will cut funding to Nonnatus House and no longer pay for the accommodation, and goes to see Violet at one of her open sessions as a local councillor. At clinic, Nurse Crane meets and cares for heavily pregnant Bonnie, who is not married but committed to the baby's father Eddie, while Kevin's dependency on pain relief is discovered by the team and Dr Turner and Miss Higgins must find a way to help him.