This novel contained a narrative that provided an explanation for the heart controversy regarding the Doctor's physiology. The narrative in The Man in the Velmet Mask stated regeneration would result in the growth of a second heart. This came about due to the apparent the presence of only one heart inside the first incarnation of the Doctor, seen in the story The Edge of Destruction, before the concept of a binary cardiovascular system was introduced in Spearhead from Space, where the newly-regenerated Third Doctor displayed two hearts in an x-ray that was taken of his chest and would become the case for his future incarnations as well as the rest of the Time Lord species.