Mark Preston (William Shatner!) and his family are terrorized by devil-worshiper John Corbis, who is trying to reclaim his Satan book the Prestons stole and have been hiding since ye olde witche tymes. Corbis gets fed up with playing games so he starts melting people and before you know it all hell is breaking loose.
So here is another awesome William Shatner horror film. It's a really creepy movie with an amazing beginning and with some really cool scenes...the best of which is when Preston challenges Corbis to a battle of faith. Both men shout prayers to their respective deities until Preston freaks out, pulls a gun, and Corbis, looking amused, asks, "Is that your faith?" And- oh what a twist- Preston loses and we switch to the real hero of the movie, his brother!
The other really awesome scene is when a church full of people melt, like devil tears in the devil's rain.
It's not all tests of faith and gooey melting people though. The flashback to colonial times is long and stupid and if they had not included it there would have been time for many more minutes of melting people. Corbis randomly changing into a devil is also awful. The makeup looks ridiculous and there isn't even any point to it. Sadly, a good quarter of the movie is made up of this terrible stuff.
But if you can put up with some dumb costumes for twenty minutes or so, the rest of a movie is a really unique entry in the genre and totally worth tracking down.