In a new video, Karen Gillan and Arthur Darvill set up this Saturday’s Doctor Who episode entitled “The Power of Three.” The episode will be a first for Doctor Who on a number of levels.

Chris Chibnall penned the episode, which is the second Doctor Who outing for him this year. He previously wrote the episode “Dinosaurs on a Spaceship.” In “Dinosaurs on a Spaceship” he introduced an instant hit with the fans, the wildly popular character of Rory’s father, Brian Williams. It’s probably little surprise that the character was so popular given that the role is played by the multi-talented Mark Williams of Harry Potter fame. When he was last seen, he was off touring the globe and beyond with the Doctor. He even manged to send Amy and Rory a postcard from Siluria when he and the Doctor presumably returned their wayward dinosaurs. Now in the latest trailer, it is obvious that Brian Williams is back for a second episode. Whether this episode is before or after his travels abroad with the Doctor remains to be seen.

Chibnall in this latest episode has done what no other writer for Doctor Who has done in the reboot era. He has written a companion point-of-view episode that is not an alternate universe. It’s the first time we will see the Doctor interacting with the companions on earth for an extended period of time, presumably for months on end. Chibnall, Karen Gillan, and Matt Smith all commented on this unique interaction in a recent interview.

Of note in the video, Karen Gillan talks about guest-star Jemma Redgrave playing a member of U.N.I.T. In the stills released by the BBC, she is referred to as Kate Stewart, which is almost certainly a character related to the late Brigadier. This will be the first time that the Ponds have encountered U.N.I.T. or any member of “The Brig’s” family.

What do you think of the idea of an on Earth episode?