The movie centers on a series of murders that are happening in the city of Las Vegas. The cops seem clueless as to who is behind these murders but Kolchak figures out it is a vampire and spend the rest of the movie trying to convince the cops he's right. The Night Stalker also has quite a bit of humor thrown in for good measure. It's not the slapstick kind of humor found in Evil Dead. It's the humor that flows from ridiculous and frustrating life experiences. McGaven delivers it completely deadpan and it works for him.
The good news is that the movie and the TV series can now be streamed on Netflix. The boxed set is a bit pricey so it's nice that The Night stalker can be seen by a wider audience. I remember watching the TV series as a kid and it scared the crap out of me...but I never missed an episode. Watching The Night Stalker as an adult makes me appreciate how well made the TV series and movie are in terms of script writing and acting. Nicely done.
For more info check out the film's entry in IMDB.