The episode begins with the Doctor, Bill, and Nardole sneaking into NASA’s command center to watch a rover probing Mars. It appears to be a routine procedure until a scan reveals a message spelled out in stones hiding under the ice cap that reads, “God save the Queen.” There is no real explanation of how the Doctor is able to pinpoint the date of origin for the message being the late 19th century, but the trio travel to Victorian Era Mars to investigate it.
They find a group of British soldiers who established a colony there. Through a lot of exposition (that would have been far more interesting to have actually seen in the episode, rather than showing men standing in a cave talking about it), we learn that the soldiers uncovered an Ice Warrior ship that had crashed on Earth. The ship contained one survivor that they awoke from hibernation and named Friday. He asked for help repairing his ship, and in return he brought them to his home on Mars so they could bring riches back to Earth.
Friday returned to discover a desolate planet. He was in hibernation for thousands of years, and in that time Martian civilization had collapsed. They find the empress and wake her from her hibernation, who in turn revives what is left of her people. They are not happy to find aliens invading their home.
As soon as danger pops up, the TARDIS inexplicably vanishes with Nardole and returns to the present day. I understand how a machine that can travel anywhere in time and space can cause problems from a writing perspective. As soon as things get dangerous, the Doctor could just bring everyone home and the episode would be over. The problem is that this just felt like a really lazy way around that. This is not the first time in a Mark Gatiss script where the TARDIS is sloppily removed for narrative reasons.
After the Doctor helps to resolve the conflict between the Martians and humans, Nardole returns; although, since he is unable to fly the TARDIS on his own, he has freed Missy from the vault to fly it.
In the final moments of the episode, we see the return of classic Doctor Who character Alpha Centauri, setting up the first time it met the Ice Warriors. This makes “Empress of Mars” a prequel to the Third Doctor stories, “The Curse of Peladon” and “The Monster of Peladon.”
I had some problems with this episode, but, overall, I enjoyed it and thought it did a great job at filling in the gaps for the history of the Ice Warriors. They originally began as villains on the show, but over time they became heroes and now we finally get to see their redemption story.