The friend was thrown in to push the serial killer angle, so I saw the reason for it. I thought the whole story of the man accused of something of he didn't do, being sent to prison, harassed and then killed was really tragic. I thought the plot was very interesting,but some parts were a bit rushed. I would've liked to have seen more about the actual killer--we usually get to see more of the guilty party than we do in this one.
The episode just felt a bit lopsided to me, like they cut stuff out at the last minute or something.
I give it a mediocre. I like the idea behind the story, but not the way it was laid out.