Pertwee’s second story features the debut of the Silurians, who would return in conflict with the Fifth and Eleventh Doctors, as well as being the predecessors of one of my favorite modern-era recurring characters, Madame Vastra of the Paternoster Gang!

https://youtu.be/_lyrIxOGhVc?si=4ujEUo2gGOB_2Bco