Nurse Jenny Lee arrives at Nonnatus House in London's East End to begin her work as a midwife. Naive and unused to the harsh conditions of the borough, she must rise above her misgivings if she is to succeed in her new role.
A new midwife, Chummy Browne, arrives at Nonnatus House, and finds it difficult to prove herself. Meanwhile, Jenny befriends a young Irish prostitute who is expecting a baby, and is shocked by the Church's treatment of the girl.
Jenny befriends an old soldier named Joe, and is disturbed by his living conditions. She is also visited by a man from her past, while Trixie and Cynthia have a sensitive case to deal with, and Chummy is asked on a date.
A new baby is snatched from her pram, sparking an area wide search. Jenny is more familiar with the kidnapper than she realizes, Cynthia blames herself when a patient becomes gravely ill, and Chummy's romance continues.
A figure from Jenny's past makes contact, while Jimmy continues to pursue her. Chummy prepares for an important meeting, and everyone at Nonnatus House rallies round the building's cleaner, Peggy, whose brother is very ill.
Jenny speaks to her ex-lover again, while Sister Monica Joan lands herself in trouble with the police. Chummy receives a visit from her snobbish, imperious mother which forces her to reconsider her relationship with Peter.
Nonnatus House is alive with preparations for Christmas. Chummy is arranging a nativity play with the Cub Scouts, Jenny is faced with a difficult case, and a young girl's predicament leads to a big decision.