S4 Demons & Terra Prime
It was also a little ironic that one of the higher ups in Terra Prime, Daniel Greaves (Peter Mensah) was sprouting the dogma and yet not that many generations back the very idea of mixing the races would have been seen in the same light as his beliefs now. I guess the underlying story was the cyclical nature of events as a society and civilisation grows both in the positive and negative aspects.
Surprisingly the gave Mayweather plenty to do in the episodes and he went with it proving he had plenty to offer if given the material but the foggy clandestine scenes with Reed and Section 31 was a little trite:)
I really did like how the handled the young Elizabeth and how it had been worked into the canon and one of the best scenes of the entire four seasons was a simple dark room, two characters from different worlds expressing loss and compassion thus making it clear where Star Trek wanted to take us.