The Doctor and the Ponds try to determine if these black cubes are the sign of an invasion on Doctor Who. "The Power of Three" is the fourth episode of the show' seventh season.
The Doctor becomes sheriff in a Western town being attacked by a cyborg on Doctor Who. "A Town Called Mercy" is the third episode of the show's seventh season.
The Doctor is the only one left to help when the Dalek ship surrounds a lone rebel ship on Doctor Who. "Into the Dalek" is the second episode of the show's eighth season.
