The original network thriller "The Night Stalker" was such a mammoth ratings hit that the following year ABC broadcast this highly successful sequel that proved the character of Carl Kolchak had the potential for still more adventures.
The approach of "The Night Strangler" pretty much follows the formula of the original tale in which reporter Carl Kolchak searched for a killer who turned out to be a modern day vampire. In "The Night Strangler", while victims are being murdered by yet another mysterious killer, the variation here is that he doesn't bite their necks but rather crushes them in his grip. Only then does he remove a small amount of blood, but drawing it through a syringe rather than with the use of fangs.
Other basic conventions carried over from the original include an action-packed sequence in which police attempting to capture the strangler discover that, like the vampire, this killer is too powerful to subdue with the use of conventional methods. There's also the climactic encounter in which, once again, it's Kolchak who tracks the killer to his lair. Oh, and of course there's the tie-up at the end where Carl is once again prevented from reporting the facts of the case.
However, distinguishing "The Night Strangler" from the original and elevating it above a simple carbon copy is the interesting back story of the killer (supplied by the imagination of the brilliant Richard Matheson). We learn here that the "Strangler" is actually Dr. Richard Malcolm, a 19th century surgeon who'd been experimenting with a method of extending life beyond normal human length. He eventually develops an elixir made from, among other ingredients, human blood.
In a scene that's both riveting and amusing, Kolchak explains his theory to skeptical police officials that the bloody trail of murders can be traced from the then present day Seattle of the 1970's all the way back to the previous century.
Indeed, Dr. Malcolm is not a ravenous vampire in search of food, but rather a mad scientist in need donors. When they eventually meet, Dr. Malcolm reveals to Kolchak that he considers these murders a small price to pay compared to the benefits that his blood-based elixir will bring to mankind.
Seattle's underground city turns out to be an inspired setting that greatly enhances the eerie atmosphere of the conclusion when Kolchak descends into it's musty depths in search of the killer. Playing the murderous Doctor is actor Richard Anderson who alternates his performance between a cultured sophistication and an explosive menace. This is probably his best work as an actor.
One other thing that sets this sequel apart from the original is the script's somewhat greater emphasis on humour amid the spooky elements. Thankfully, this works quite well without diminishing the suspenseful aspects of the story. Particularly memorable are the scenes between Kolchak, the reckless, pit-bull of a character who refuses to give up on his story, and Tony Vincenzo, the harried newspaper editor more desperate to please his employers than in committing the professional suicide of backing his ace reporter. Their exchanges are extremely funny and actors Darren McGavin and Simon Oakland carry them off with great élan.
Of course it's debatable whether "The Night Strangler" is actually a superior film or more frightening than "The Night Stalker". Certain touches in the original (like the vampire's hungry, black eyes presented in spine tingling closeups) are perfect, indelible and hard to top.
There is a case to be made that silent characters just seem more mysterious and frightening than those who have a lot to say (like "The Night Strangler's" more loquacious villain). The vampire of the first film doesn't utter a single word, but instead hisses like some vicious beast and this makes him seem more alien in nature than the refined, well-spoken mad Doctor. At the same time, the Strangler crashing through a window to attack a young girl is a pretty startling moment, too, as is his degeneration at the end into a living corpse. Indeed both films contain some undeniably memorable chills courtesy of their titular characters.
It does seem the over-all tone of the "The Night Strangler" (with it's well balanced, dead-on ratio of humour to horror) is what the subsequent "Kolchak: The Night Stalker" series most seems to have been trying to emulate. If you're interested in that series, you can click on the a_l_i_e_n link for reviews of all 20 episodes.