CONTAINS SOME SPOILERS
To be honest, you're asking for trouble setting any horror movie over one of the seven gates of hell or one of the seven doors of death. Such things are the stomping ground of wonky Italian horrors of the late 70s and early 80s, particularly Lucio Fulci, whose unique blend of morbid darkness, excessive gore and plots that make no sense has always been a curiously agreeable mixture. The Beyond is even known as Seven Doors Of Death in America, and for all that's wrong with that film the bar is set pretty high.
Nightworld is too well-behaved to go down the Fulci route, save for the morbid darkness. It's mostly goreless (it would most likely get away with a 15, and not a top-end one at that) and its logic more or less hangs together except on one point. Following personal tragedies, Brett (Jason London) takes a job as a security guard at a Sofia apartment block, a shining example of a building you would never want to set foot in in the real world. There's apparently no-one else in the block except for a maid, who is only seen once: no-one appears to actually live there and underground there's a vast hangar that is kept permanently locked. So what are the occasional shadows that show up so briefly on the CCTV feed?
The point at which the logic collapses is when Brett calls it in to his superiors, who respond by sending in an elderly blind man (Robert Englund, having fun) to investigate what's on a video tape. It does also falls victim to the old trope of characters encountering people they know to be long dead but suddenly not being bothered by the fact that they're ghosts or zombies, and wanting to stay with them rather that doing the sensible thing and getting the hell away from them. But it's generally pretty decent: a nice creepy setting, dark and doom-laden, with a good sense of imminent apocalypse, and I enjoyed it enough.