An adult version of 'Doctor Who' where they deal with mature subject matter. I liked the main actor and much of the first season. It was nice to see Marsters back in action for a couple of episodes. It suffered the same fate that 'Dr Who' in the declining quality of the writing.
The first two series are meh at best (but with lots of bisexuality, which is nice). Series three is amazing (with a great Peter Capaldi role), and series four had an interesting premise, but was just a relatively weak execution. Jack Harkness is fun and all, but this doesn't really need to come back.