This is part of a series of reviews of Doctor Who in chronological timeline order.

Previous Story: Medicinal Purposes

This is such a bizarre story, I can't really think of any stories to compare it to. Maybe Midnight? But even then that's only really at the start. I will say, this is one of the more compelling mysteries I've heard in a Doctor Who story. It brings up a really interesting idea that there were countless other sentient species that evolved on Earth. But not like Silurians in that they evolved and existed in a different time to humans but instead that they were ocmpletely erased from time. It's really interesting and genuinely quite a scary thought, that there are completely different species that evolved like us, but nothing like us.

There's a point where the Doctor goes back in time, to a midnight train heading to some military base in the middle of the Cold War. This is a very atmospheric setting with the constant sound of the train, we've got a fairly small cast and I'm not sure how to explain it other than it feels cozy. On this train is some sort of scientist, not a famous one or anything but apparently he's idly sketched the basis for humanity's ability to travel the stars. It's a fascinating idea and it's likened to Da Vinci sketching helicopters and things like that. The reason this whole bit is in the story is because one of the many species erased from time has been preventing every other Earth species from travelling beyond the solar system and has now hitched a ride through Evelyn in the TARDIS so that it can go back and destroy these sketches, thus preventing humanity from achieving interstellar travel.

I thought the ending was a bit simple for stakes of this magnitude, but I don't particularly mind it and the rest of the story builds up such a compelling and haunting mystery that it could've ended with just about anything and I wouldn't have minded. Definitely one of the most inventive stories I've heard in ages.

Next Story: Pier Pressure