Every story line follows from the previous one. The solution for each episode produces a problem for the next episode–at least most of the time. This gives it a very organic, true feeling flow to the action. This bad thing happens to the characters and in their attempts to fix this bad thing, other bad things flow forth.
There is dry humor. Something that is always a favorite of mine.
They do indulge in some clichés but debunk others. They are going to kill only bad people for her to eat. Yet when they pick out people they often find they were wrong about the person and change their minds.
The into is short. None of the time-consuming credits and fancy special effects repeated each time. It is a 30 min show and they use every minute.
Plus the actors are good. No real deadwood there. (Yes, pun intended.)
An all is lost moment occurs at the end of season one when they think they are on the road to a cure but then it looks like that is not going to happen. Does leave the story line open for next season.