Trixie's feathers are ruffled when Jenny is promoted, but the new Acting Sister has more to worry about after a mother-to-be reveals the baby she is carrying doesn't belong to her husband - and to complicate matters, the real father is black. Cynthia is inspired by a lecture on natural childbirth, convinced it will help an overly anxious patient, while Alec and his friends try to persuade Jenny to join them on a CND march.