Christmas is coming, and in Poplar the midwives of Nonnatus House are busier than ever. When an abandoned baby is discovered on the steps of the convent, the whole community rallies round to provide food and clothing, and to try and trace his mother. Nurse Jenny Lee (Jessica Raine) meanwhile, gets caught up in the heartbreaking mystery that surrounds an elderly, semi-vagrant local woman, Mrs Jenkins (Sheila Reid). For newly married Chummy (Miranda Hart), other challenges await, as she pulls out all the stops to mount a truly memorable children's nativity play.