In ancient Byzantium, Emperor Justinian is interrupted in the middle of a rather desultory orgy (the IMDB write-up for this movie includes in the Goofs section, "Ancient Rome did not have the technology for the silicone breast implants shown in the opening scene") by the arrival of his other lover Dhani, who has discovered an even more ancient Babylonian magical book that will give its wielder ultimate power and is presenting it as a gift to the Emperor. Justinian rather understandably points out that he's the Roman freakin' Emperor, so he pretty much already has ultimate power. Dhani insists, however, so he drags himself out from under the women draped over him and slices open his hand to bleed on the book. A mysterious blue glow filters out of the book and into his body, causing every woman in the scene who was still wearing one to rip off her shirt and throw herself at him.
Cut to 21st Century LA, where Nina is celebrating her 19th birthday. Tonight, the boy who has a huge crush on her is throwing an even huger party. Also her aunt, who she lives with, has something important to tell her. But first it's off to philosophy class for a debate on power vs. cooperation, which is clearly intended to set up some deep philosophical themes which would have been addressed throughout the movie if the writers hadn't immediately forgotten about them. Then it's time to go back home, where a portal opens in her bathroom and sucks her through to Hell. Hell is apparently an abandoned school, where people are being tortured in various ways. Eventually, Nina stumbles across a Nazi soldier -- doomed to be cremated alive over and over by the Jews he murdered -- who has repented of his crimes; he mistakes her for an angel and tries to confess his sins to her. She's having none of that but she does leverage his desperation to get him to tell her the way out -- which turns out to be "go back the way you came and exit through the portal that brought you here," which you kind of think she might have been able to figure out on her own without chatting up a Nazi.
Back in LA, Nina's aunt fills her in on her (and the movie's) backstory: Nina isn't really her niece; instead a mysterious old woman left her on the aunt's doorstep shortly after she was born, along with a mysterious book. The aunt spent the next nineteen years learning Latin so she could translate the book. It turns out the book gave Emperor Justinian ultimate power not only in life but in the afterlife, as well. He shared this power with his wife, Empress Theodora (Carmen Electra), and their lover Dhani. The only catch -- every new moon, they each had to sacrifice 100 people to maintain their power. Eventually the daughter of Justinian and Carmen Electra rebelled. Justinian killed her, but as she lay dying she spit on Justinian, giving him the Justinian plague, aka the Black Death, which went on to wipe out 90% of the population of Europe. Although their power protected them from the plague, eventually Carmen Electra, Dhani, and Justinian all died of various causes and the plague burned itself out. But Nina is a direct descendent of Justinian and Dhani and is afflicted with the Emperor's curse -- if she doesn't kill herself in the next three days, she'll come down with the Justinian plague and infect all of humanity.
That's a lot to take in. But first, it's paaaaarty time! Did we mention it was a toga party? We now interrupt this movie for a 30-minute digression into Animal House. There are no horror elements, no sinister premonitions, and no boobies (since we already got plenty of those in the Byzantium flashbacks). But we do have all the teen party comedy stereotypes: the obnoxious football players; the long-haired drug dealer; the completely wasted best friend; the slutty girl; the attempts of various characters to get laid only to be thwarted at the last second by some random coincidence; and the shy nerdy guy who's only throwing this party to impress our heroine, who is happy to talk to him but who is absolutely not going to sleep with him because she's "not that kind of girl." Wait, this is an occult horror movie and the heroine is a 19-year-old virgin? Gee, do you think that's going to be an important plot point? Well it isn't, because, like so many other things in this movie, the writers set it up and then immediately forget about it. Anyway, eventually the drunk best friend hurls all over Nina's white toga and she goes off to the bathroom to change into something less barfy and get sucked through a portal to Hell.
Back in LA, the party reaches its climactic seance, which wants only an object with a strong psychic resonance. Fortunately, the drunk best friend has anticipated this need and swiped the Nazi medal that Nina's (supposed) grandfather took off a Nazi guard he killed while liberating a concentration camp in WWII. Gee, I wonder which Nazi that might turn out to be? The seance opens another portal to Hell and attracts the target Nazi's attention, but before he can be drawn through, Justinian, Carmen Electra, and Dhani come through instead. This marks our foray into the teen slasher genre, but we're also almost out of time, so the three Romans kill off the entire set of party guests in significantly less than two minutes in what has to be the most half-assed teen slasher scene ever committed to film. Meanwhile, back in Hell, Nina stumbles upon the plague-ridden daughter of Justinian and Carmen Electra, who tells her that the only way to defeat Justinian and his polycule is to burn the book, destroying the source of their power. Although we last saw the book in Nina's bedroom in LA, she conveniently finds it in the next room over in Hell. Now that she has the book, she just has to find a fire to destroy it in before Justinian and his friends with benefits get back. Gee, if only there were a handy crematorium around here somewhere...
