Heidi gives birth to Satan's child and becomes Satan's new bride.
The film opens in the 1600s in Salem, Massachusetts. Reverend Jonathan Hawthorne declares war against a coven of witches that he refers to as "the lords of Salem,"claiming that they make unholy music in the name of Satan. In the woods, meanwhile, we see a coven of witches led by Margaret Morgan (Meg Foster) who are indeed praying to and rejoicing the Devil. They watch as one of their members gives birth to a child, but Margaret is incensed once she determines that the Satan is not the child's father.
The film cuts to present day Salem, where Heidi Hawthorne (Sheri Moon Zombie) is walking her dog. She lives in a largely empty apartment building with her landlord Lacy Doyle (Judy Geeson) and Lacy's sisters Sonny (Dee Wallace) and Megan (Patricia Quinn). Heidi is a recovered drug addict who works as a radio DJ named "Heidi LaRoq" along with her co-hosts Herman "Whitey" Salvador (Jeff Daniel Phillips) and Herman Jackson (Ken Foree). It is apparent that Whitey is in love with Heidi and that she is flattered by his affections. One night, Heidi receives a package containing a record from a band called "The Lords" (Herman Jackson later refers to them as "The Lords of Salem"). When she plays it, she becomes transfixed, seeing visions of Margaret Morgan's coven.
The next night, the radio show hosts an author named Francis Matthias (Bruce Davison) who has just written a book on the Salem Witch Trials. The DJs play the Lords of Salem record on air and, unknown to them, several women throughout the town become transfixed. Meanwhile, the record makes Heidi sick and it troubles Francis. Heidi goes home and has wine with Lacy and her sisters. Megan, a palm reader, looks at her palms and informs Heidi that she has a strong line marking her "fate," noting that no matter how much Heidi may struggle, she can't change fate. That night, Heidi has a dream where she walks into one of the abandoned apartments and meets with a beast-man (probably Satan).
Things begin spinning downhill for Heidi. She is having horrific visions involving witches, demons and fallen angels who rail against the "butchers" of Heaven. Meanwhile, Francis remembers that the term "Lords of Salem" refers to Margaret Morgan's coven. He recounts that Reverend Hawthorne had burned the coven members at the stake before putting Margaret herself in an iron contraption and feeding her to the fire. Knowing that his knowledge is incomplete, Francis contacts an expert who read Reverend Hawthorne's diary. The expert tells him that before she died, Margaret cursed the descendants of the women of Salem (who Hawthorne was seeking to protect) and prophesied that Hawthorne's own descendant would one day become the mother of Satan's child. Francis does some research and determines that Heidi is the last living descendant of Reverend Hawthorne.
Meanwhile, Heidi has become far more sick and has also relapsed to drugs. She is cared for by Lacy and her sisters, who as it turns out, are worshippersof Satan. Heidi's satanic visions grow stronger and are now being triggered by the sisters. Francis arrives at the apartment building to talk to Heidi, but he is killed by Sonny (head bashed in by a frying pan). Meanwhile, the Lords of Salem are giving away tickets through the radio show for a one-night only performance hosted by the DJs.
The night of the show arrives and Whitey comes to the apartment to take Heidi. The sisters consider killing him, but after realizing that Heidi loves Whitey, they spare his life. They arrive at the concert venue where Herman waits for them outside. He is angry, believing that Heidi has been abused or has relapsed. While he and Whitey argue about what to do, Heidi sneaks inside the venue and locks the men out.
There are only about 30 women in the audience in addition to Heidi. The show begins and it is revealed that Lynn, Sonny and Megan are the band members. They begin to chant to Satan as the audience members become transfixed. Margaret Morgan is resurrected by the sisters and the women all become engaged in acts of erotic hedonism and revelry. Heidi then gives birth to a tentacled demon and Margaret Morgan lovingly embraces the child as the heir of Satan. The sisters then smile with tears of joy in their eyes as they see a transformed Heidi as Satan's bride, standing atop a pile of the women's corpses.
As the credits roll, a news report states that all the women who attended the concert were found murdered the next day. It turns out that all of the women were descendants of the villagers of Salem that burned Margaret Morgan and her coven. The report notes that Heidi is still missing. It appears that Margaret Morgan's curse/prophesy has come true in full.
Thanks Evan B!