I give this one a solid 8 and would have given it a 10 if they hadn't drawn it out because I think the series could have wrapped up in less time. Anyway, the two main characters, wow are they sociopathic clever I'll give them that one. I don't want to add details because I don't want to spoil it, but the twists in this, the sheer creepy natural style of the two makes the hairs on your neck stand up. I can only say that I wish the crime investigation tech of today had been available back then. I watched this in a morning (I wake up really early) and couldn't stop. The investigative side and commentary woven in makes this a well done documentary. I'll say remember one word 'passion'...in more ways than one.
