Protests on the Isle of Dogs cause chaos for the Nonnatus team, while an apparent immaculate conception concerns the midwives. Sister Julienne and Trixie plan to fight back the Board of Health's disapproval of the way Nonnatus House operates.

Call the Midwife follows the nurses, midwives and nuns from Nonnatus House, who visit the expectant mothers of Poplar, providing the poorest women with the best possible care.