There are movies that go for broke, and then there’s Lifeforce, Tobe Hooper’s $25 million Cannon Films epic about space vampires, psychic sex, exploding bodies and the eventual destruction of London. It is huge, strange, sometimes genuinely terrific and frequently so overstuffed that you wonder if anyone involved ever considered saying, “Maybe that’s enough.” Thankfully, producers Menahem Golan and Yoram Globus were not generally known for saying that.

The crew of the space shuttle Churchill is investigating Halley’s Comet when they discover an enormous alien spacecraft hidden inside its coma. Inside are three perfectly preserved humanoid bodies, two men and a woman, which naturally seem like the sort of thing you should bring back to Earth. The female of the trio (Mathilda May) eventually wakes up in London and begins draining the life out of anyone unfortunate enough to get close.

SAS Colonel Colin Caine (Peter Firth, Equus) gets pulled into the investigation, while Churchill commander Tom Carlsen (Steve Railsback, The Stunt Man) reappears with a very personal connection to what has been unleashed. Frank Finlay (Neither the Sea Nor the Sand) plays Dr. Hans Fallada, and Patrick Stewart (Green Room) turns up as Dr. Armstrong before things get considerably weirder.

Dan O’Bannon, who co-wrote Alien, and Don Jakoby adapted Colin Wilson’s novel The Space Vampires, which is one of those titles you’d think Cannon would have been thrilled to keep. The movie became the first of Hooper’s three pictures for the company, arriving three years after Poltergeist, while Henry Mancini, of The Pink Panther fame, supplies a score so grand it sounds like nobody told him he was composing for naked extraterrestrial vampires.

The opening stretch is easily the movie at its best. The discovery of the alien ship has an eerie sense of scale and mystery, with Hooper mixing science fiction, Gothic horror and old-fashioned exploration into something genuinely creepy. The spacecraft itself is a terrific design, reportedly inspired in part by an artichoke, because of course it was. Once everybody gets back to Earth, Lifeforce starts mutating almost as quickly as its vampires. What begins as an extraterrestrial horror story adds psychic possession, body swapping, apocalyptic plague, military action and increasingly elaborate mythology until the screenplay feels like it’s racing to explain ideas faster than it can invent them.

That’s where the movie starts losing me, but it’s also where its lunacy becomes part of the appeal.

Railsback gives Carlsen an intensity that borders on radioactive, seemingly one emotional jolt away from flying out of the frame. May, who was just 18 when the film was made, is required to spend much of her screen time completely nude, but the movie treats her character less like a conventional seductress than some strange, unknowable force walking around in human form. Firth deserves special credit for anchoring all of this with remarkable seriousness. No matter how ridiculous the latest revelation becomes, Caine reacts as if this is simply another unusually difficult day at the office.

The movie also has scale that’s increasingly hard not to admire. Practical effects, enormous sets and large-scale destruction pile up as London descends into chaos. Parts of the ruined city were even built using remnants of Tucktonia, a defunct model village, which somehow feels exactly right for a Cannon production that seems determined to turn whatever it can find into spectacle.

Hooper shoots the whole thing as though someone has handed him an absurd amount of money and neglected to mention that it might never happen again. There’s something exhilarating about that. Even when Lifeforce becomes a mess, it is a mess built with armies of extras, elaborate makeup effects, exploding sets and complete confidence that audiences are dying to see a naked space vampire suck glowing blue energy out of people.

The trouble is that enthusiasm doesn’t automatically make the movie work. The middle drags under the weight of all that mythology, and at 116 minutes the International Cut can feel considerably longer once the clean simplicity of the opening gives way to one supernatural wrinkle after another. The shorter theatrical cut moves faster, but it also trims material that helps the story make more sense. Pick your poison.

Audiences weren’t especially interested in either option in 1985. Lifeforce opened in June and earned roughly $11.6 million domestically against a much larger budget. Wilson wasn’t particularly thrilled with what became of his novel either, but home video eventually gave the movie exactly the kind of second life that cult films need. I can certainly understand why. Even when I’m not completely enjoying Lifeforce, I’m fascinated by it. There is simply too much money, craft, lunacy and naked ambition splattered across the screen to dismiss it.

Trying to make Lifeforce behave like a sensible movie is probably the wrong approach. Accept it as an enormous Gothic space opera where vampires arrive with Halley’s Comet and London eventually pays the price, and the whole crazy thing becomes much easier to appreciate. It’s still a mess. But what a mess.