Series 5 was broadcast on TV in 4 episodes, each of which were 90 minutes long, but this was edited to 6 episodes of 60 minutes each for DVD release. So originally Rachel's death came at the end of episode 3 rather than the middle of episode 5. I too watched it as 6 episodes of 60 minutes and I think it works rather well, as Adam's dad becomes a recurring character and the aftermath of Rachel's death in episode 5 is really fitting I think. Hope this helps.