Aliens, and Jurassic Park) is a morality tale wrapped up in a no-frills monster movie. It's no masterpiece, but it gets the job done.
Ed Harley (Lance Henriksen) owns a way-out-in-the-country grocery store and dotes on his young son, Billy (Matthew Hurley). One day, while Ed is away, a bunch of teens from the city arrive with dirt bikes, and in a freak accident, Billy is run over and dies. The teens, save for one who waits for Ed, take off for the cabin they're staying in. Distraught to find what happened to his boy, Ed remembers an incident from childhood and seeks out the witch Haggis (Florence Schauffer). She can't raise the dead, but she can grant him vengeance; she can summon a demonic monster known as Pumpkinhead. All it will cost is Ed's soul.
No, the monster's head is not a pumpkin. The reason he's called Pumpkinhead is because the witch sends Ed out to a pumpkin patch to dig up the body she intends to use as the monster. Pumpkinhead himself resembles the xenomorph from Alien, albeit paler and more skeletal, but like that creature, Pumpkinhead is a convincingly lifelike monster and a nasty piece of work. Winston doesn't show him off too much, shrouding him in shadows and showing him from a distant, so we can tell he's there but can't make out his features except in closeups.
Execution-wise, the movie is by-the-numbers, cutting back and forth between slasher scenes and scenes in Ed realizes the wrong he's done. Pumpkinhead picks the kids off one-by-one until there's a climactic showdown. Pumpkinhead is shown to be literally invulnerable, so there's a lot of running around and screaming once it's established that trying to fight him is pointless. It would have helped the movie immeasurably if the teens were better defined and distinguished, but they're a pretty bland, boring bunch. Sure, there's the couple who try to do the right thing, and the jerk who ran Billy over eventually decides to turn himself in (before Pumpkinhead shows up), but it's not enough, especially when the transition from I-ain't-going-to-jail to I'll-come-clean occurs off-screen.
Ed, by going to the witch and summoning a monster, probably thought revenge would be sweet, simple, and something he could be distant from, but the spell binds his soul to Pumpkinhead. Psychically, he can feel the murders, experience the pain, terror, and death, and it is not pretty. When he realizes what's happened, Ed tries to call it off, but Haggis laughs, telling him it's got to run it's course. By the end, Ed finds Pumpkinhead looking like him and himself looking like the monster. The ugly face of revenge can be seen by looking in the mirror.