This is a very fun episode, but bar the ending it's pretty much just 'Martha Jones joins Torchwood'. There isn't really much to the plot - and that's fine. Sometimes it's nice to have a story that's more about the characters than the alien situation.

The end took me totally by surprise though. I wasn't expecting that. After all the stuff they've been through, to have one of Torchwood taken out simply by another human being is quite tragic and shocking to see. It's such a strong way to end the episode.