The basic plot involves the Templar knights who, in this film, hoped to obtain eternal life by drinking the blood of human sacrifices. Fast forward several hundred years to modern day Portugal where the Templars are brought back to life to terrorize the countryside. It sounds interesting. However these zombie knights evoked no emotional response in me whatsoever. The main problem with the costumes is that you never see their eyes or mouth. They have a blank, unexpressive, armored face. It just doesn't work for me.
Tombs of the Blind Dead is a Spanish film dubbed into English. Even if you're a die-hard zombie fan, you might want to consider skipping this one. There are better ways to waste an afternoon or evening!
For more info check out the film's entry in IMDB.