Although not common today, rickets was a serious disease affecting children in the 18th Century, manifesting itself in a softening of the bones. The primary cause is Vitamin D deficiency caused by diet or lack of sunlight and deprivation of calcium, magnesium, and phosphorous. Dietary supplements of milk, butter, eggs, and oily fish are recommended.
Michael Cadman as Dr. Enys has a line to Caroline when he meets her after being rescued: "I'm not the same man who went away!" In context that is both a figurative and a literal statement. In previous episodes he was played by Michael Morant.