1. John Simm...he has so much to do in this episode. In all the episodes, really, but this episode gives us a glimpse into what he has to play: dry humor ("From the diary, quote, 'I killed her. She's been killed. I'm a killer, an ace killer.' That particular entry is not awash with ambiguity.'), frustration and coldness (saying feelings have no place in their world), total confusion, hope, fear, on and on.
2. Philip Glenister: The energy between JS and PG is just amazing. And of course, playing Gene Hunt must be so much fun; energetic, bastard-y, hilarious, completely rude. Gene represents everything that is wrong with the 70s CID while simultaneously representing everything that's wrong with the 2006 CID.
3. The music works so well in this show...especially the Bowie here bridging the "cross-over" between present day and the 70s.
4. The little boy who played the younger Colin Raimes? Possibly the creepiest looking child on TV since the Olsen twins. *shudder*
I'll have more thoughts, but that's what I've got for now.
Mycroft: Just once, can you two behave like grown-ups? John: We solve crimes. I blog about it, and he forgets his pants. I wouldn't hold out too much hope.