Mark Gatiss' script reintroduces the Ice Warriors from the original series, the warrior class from the dying planet Mars, and fuses them with a version of "The Hunt for Red October" on a Soviet nuclear submarine in the 1980s. That may sound like a pointless hodgepodge, but bear in mind that Doctor Who is science fiction and below the surface of the best episodes lurks a symbolic message. Here, it is about the conflict between ideology and personality: the Ice Warrior who believes himself the last of his race and so bound by his warrior's code; the submarine's captain who does his job, but is privately tired of war; his second officer who longs for a war, regardless of the consequences; and David Warner as a research scientist who is a pop music fan. Warner's performance is the standout, but Gatiss' scripts tend to have great star turns and Warner has a lot of fun with the role.
The story is exciting and terrifying in its appeal to a real world threat that still lurks in the psyches of the members of the audience who grew up during the Cold War: the helpless fear that someone would push the button and the world would end, with nothing we could do about it.
I've commented before on the great job that the cinematographers have been doing this season. Here it's Suzie Lavelle in her first episode. She has taken the monochromatic spotlight gels originated by Ernest Vincze and used a combination of fish-eyed lens, a jittery moving camera and the narrow corridors of the leaking, sunken submarine to underline the paranoia. It's a brilliant effort. Although she is not shown as the director of photography of any other episodes, I hope we get to see more of her work.