sorry to be a slow coach; Caught up with the last two episodes last night. I knew what was going to happen as couldn't resist reading this thread. Even being pre-warned, I was just gobsmacked at how dark it was. I basically cried for most of the last episode and couldn't watch the bit of poor stephan.
I think it was so upsetting because it just felt like it would happen like that, and that it has happened within living memory. Human nature is not a pretty thing.
The bit that annoyed me was how did Jack think that first time round he would be able to stop the alien? By just saying 'Stop'? And the alien would go 'it's a fair cop guv' and go home.