In this episode we see more of Mickey & Jackie and find out more about their background and relationship. The Doctor must make the ultimate sacrifice as he has the choice: death to him, Rose and the Slitheen or death tot he world.
Of course Rose and the Doctor wouldn't die so early on in the series so it answered the question before we found out.
Once again there is a bit of silly humour but that gets better as we get to more serious conversations.
For the first 2 parter, episodes 4&5 weren't that bad and I am glad they did it.
All in all, a good episode.