A solid enough story bolstered heavily by some incredible performances. Eve Myles in particular is a standout. The entire aftermath of Rhys' death and how she plays Gwen in that situation is truly heartbreaking.

I think the growth of the main Torchwood team as a true ensemble cast grows throughout the series and really culminates here, especially with both audience and characters' relationship with Owen, which was needed to set up the second series. And Janto. Janto's always nice. 

A nice way to tie in to series three of Doctor Who at the end there, as well.