A slow episode, but some good SF, and a really nice use of unusual elements in the children. But there are some strange missteps on the way.
The most obvious: why would you make this an exact duplicate of Earth? It serves no plot purpose, other than to try and justify exactly why the culture and language exactly match. But it didn’t serve any purpose other than that, and seemed like a big point just left hanging.
That said, the use of the children was interesting. A group of children can create quite a sense of menace when used like this. The concept of the virus that kills adults (‘grups’) was interesting – I’m not sure that’s how society would actually evolve, as I’m not that sure that adolescence is that big a factor. But good SF is meant to be thought provoking.
One final thought: it’s pretty clear that there’s nothing that looks like the Prime Directive in place at this time. They land, cure the society, and then send in truant officers!
8 down, 729 to go.