The Devil's Rain is decidedly the latter. Which is a damn shame, because it has so much going for it.
First, there's the cast. When you have William Shatner, Ida Lupino, Tom Skerrit, Keenan Wynn, Eddie Albert, AND Ernest Borgnine (as a goat-man devil worshipper - !!!), your film simply CAN'T suck, can it? Sadly, it can, and this one does.
Second, I'm a big believer in the notion that there are no bad ideas, just bad executions of ideas. If you look hard enough, you can see the potential in this story, and perhaps pieces that other filmmakers turned into honest-to-goodness decent films. The scary, powerful book reminds me of the Necronomicon in The Evil Dead. The reincarnation of Corbis was reminiscent of the reincarnation of Pumpkinhead. There's a good movie in here somewhere, but the writer, director, and Satanic consultant they hired for this film can't find it with two hands and a flashlight.
Third, this movie doesn't hold back on the gross. Not blood, but there are some rather cool and disgusting melty effects. I almost never get physically, literally sick at my stomach watching movies, but the extended meltyness at the end made me seriously queasy.
The main thing that's wrong here is the story. It's incomplete, first and foremost. It's like the screenwriters were telling the story in their own heads and only put half of it down on paper, and not even a cohesive half, but scattered bits that just add up to a half.
We start with a bunch of close-ups of Heironymus Bosch paintings and the sound of people moaning in agony over the opening credits. These take far too long, by the way, and if you're padding your film out in the credits, this is not a good sign for things to come. In the opening scene, Emma Preston (Ida Lupino) worries a lot and spills hot tea all over a man named John. Her son Mark (William Shatner, still carrying the Star Trek cuteness) returns home, having gone out to look for his father Steve, but without success. Steve returns, looking very waxy-faced, and tells the family to give "the book" (whatever that might be) back to Corbis (whoever that might be), before quite literally melting into a puddle of goo right before their (and our) eyes.
Emma wants Mark to take the book to Corbis, but he won't do it. So she tries to give him a huge, clunky amulet instead. Daddy's truck returns driverless, but there's a voodoo doll on the steering wheel that is presumably meant to be Emma. Mark goes back to the house to find John hanging upside down and screaming like a little girl and Emma missing, prompting him to scream
Next there is some more movie padding. Landscape. Slow driving. Stopping to wipe brows and look at the scenery. More slow driving. Slow pulling into places. Church. Ghost town. House. I swear there is even some rolling bramble (it's the West, y'all!). Then he meets an incredibly winky Ernest Borgnine, who he doesn't realize at first is the latest incarnation of Corbis. Mark proposes a duel of faiths - his mother and father returned to him if he wins, the book and himself to Corbis if he loses. After lots of random satanic ritual stuff, Mark loses the battle, presumably too freaked out by the weirdness and Corbis's insistence on calling him some strange name to do anything but shoot panicky bullets from his gun and try to run away before finally being captured.
Random, sudden cut to Dr. Eddie Albert and his assistant Dr. Tom Skerrit, Mark's brother (conveniently named) Tom. There's some meaningless parapsychological babble, and Tom's wife Julie speaks psychically while having visions of what's happening to Mark. SCREEEAAM! End scene.
Tom bickers with Sheriff Keenan Wynn and goes to the ghost town after his brother, after leaving a message with the clearly incapacitated John. Meanwhile, the ritual to bring Mark to the dark side has begun. Tom and Julie arrive and find the "church" where the ritual was taking place and Julie (I think) recognizes it (eventually) from her visions. Tom finds Mark's shirt, helpfully labeled "Preston," before they hear an explosion and go outside to find their car has blown up.
Tom finds a satanized John Travolta (in his very first film), and Julie looks into his black devil eyes to find a flashback to Pilgrim times, where some familiar faces let us know that the Preston family has betrayed Corbis by taking the book several hundred years ago and turning him over to a burn-at-the-stake mob.
Tom sends Julie back home in Mark's car, but newly satanized Momma is waiting for her in the back seat in what turns out to be the only real scare in the movie. Tom then inexplicably watches the last of Mark's ritual without saying or doing anything to help or even reacting much in any discernible way.
There is then some rather stunningly bland exposition with Tom and Dr. Eddie Albert, and the audience is left to wonder how the hell they know about any of this or figure it out at all. But it's too late for the story to follow any kind of logic, so we move on to yet another ritual, this time with Julie. While that's happening, Tom and Eddie find the eponymous Devil's Rain - a big jar that contains the souls of everyone whose name is in the book. This is a fairly good effect for 1975, I must say, with the window of the jar looking like a distorted television screen showing people clawing and moaning and reaching. Sadly, the rest of the movie is nowhere near this dubious calibre.
And then comes the climax, and if you thought the rest of the movie made no sense, you ain't seen nuthin' yet. I'd try to explain it, but I'd fail almost as badly as this film does in the end. I'd say if you want to watch this movie at all, though, the last 20 minutes are really the only parts worth watching. And probably 10 minutes or more of the last 20 are some of the grodiest, and definitely the waxiest, meltiest images you have ever seen. It ultimately takes too long, is not worth watching for the amount of time it lasts, and is definitely not worth sitting through the other 80 minutes of the movie, but it's pretty spectacular nonetheless.
Now, I've got nothiing against wacky movies that make no sense. William Girdler's The Manitou, for example, is pretty awesomesauce. But The Devil's Rain is like crack jelly scraped over too much bread. There's a little to enjoy, but not nearly enough to justify a feature length film.
Bonus Lameness: The tagline for this film, which is on all the posters and is even spoken in the trailer, is "Heaven help us all when THE DEVIL'S RAIN." There is so much grammatically wrong with that sentence, I can't even begin to explain it, except to ask "When the Devil's Rain what?"