Sleepwalkers has the dubious distinction of being Stephen King's only original theatrical screenplay (he wrote a few other original pieces for TV), and it's easily one of the worst King movies ever made, just laughably bad pretty much from start to finish, writing included. It's not all King's fault -- the performances range from inoffensive to dismal (lead actor Brian Krause is especially awful), and the direction from longtime King associate Mick Garris is flat and hokey. The special effects look ridiculous, and the pacing is totally off. Even the concept is silly: Sleepwalkers are vampire-like creatures who feed off the souls (?) of female human virgins, and are vulnerable to cats. So Krause's Charles and his mother Mary (Alice Krige) roll into town, stake out a nice virgin, then let Charles seduce her and suck out her sparkly essence so he can pass it along to his mom.
At least I think that's what's supposed to happen -- it's kind of unclear, but the pair do show up in an Indiana town where Charles enrolls in high school and cozies up to the wholesome Tanya (Madchen Amick). There's a somewhat creepy, atmospheric vibe to the early part of the movie, and the incestuous relationship between Charles and Mary, while a little self-consciously edgy, gives the movie a bit of darkness. That all goes out the window pretty quickly in favor of cheesy one-liners, bumbling cops and invisible cars, and once Charles and Mary morph into their true monster selves, the movie just becomes a complete joke. The saddest part is watching all the cats as they swarm around Charles and Mary in the movie's climax; they look like they are literally being flung at the actors from offscreen. At least their performances have a bit of naturalism to them, which is more than you can say for any of the human performers.
How far to Castle Rock: Although the movie takes place in small-town Indiana, not Maine, the school buses and cop uniforms indicate the setting as Castle County, and one cop mentions bringing in reinforcements from Castle Rock.
King cameo: He gets a couple of lines as the caretaker of the local cemetery; Clive Barker, Tobe Hooper, Joe Dante, John Landis and Mark Hamill all appear in bit parts as well, but even their combined powers can't save this mess.