A team of astronauts finds a giant alien spacecraft hidden inside of Halley's Comet. Within the enormous craft they find the corpses of thousands of weird bat-like creatures, as well as what appears to be three peacefully sleeping naked people (one of them a hot-ass lady). All but one member of the crew dies under mysterious circumstances, and the naked alien people are brought back to Earth for study. What are they? Motherfucking space vampires, that's what, and they intend to conquer Earth by sucking away our lifeforce and turning us into their exploding zombie slaves.
To call Tobe Hooper's output inconsistent would be generous, but I would rank Lifeforce amongst his best films. If nothing else, the man can pump up the visual style, and Lifeforce is a treat for the eyes, trippy and jam-packed with unconvincing but fun 80's special effects. You get a cavernous alien spacecraft, swirling vortexes, emaciated exploding space zombies, vampire blood that erupts out of Patrick Stewart's face and transforms into a naked lady. And so forth.
The insanity of the story (co-scripted by Dan O'Bannon of Alien, Dark Star and Return of the Living Dead fame) adds much to the fun. I was expecting naked space vampires, but I wasn't expecting demonic possession, psychic mind powers, bat monsters or a zombie apocalypse to factor into things. It's overlong and overstuffed but that's all part of its charm.