A lot of this episode was clearly set-up for the final two episodes, which is no bad thing, but meant some of it dragged. I also don't think John Barrowman is all that great an actor, something that doesn't come up much in earlier (dare we say, less good) Torchwood, but is very evident when he's acting opposite Peter Capaldi

Still, though, Children of Earth remains some of the best Torchwood yet, with the scenes between Frobisher and the 456 being very strong highlights