In Salem, Massachusetts, Heidi (Sheri Moon Zombie), a recovering drug addict, works as a DJ at a hard rock station with her co-workers Whitey (Jeff Daniel Phillips) and Munster (Ken Foree). She receives a strange wooden box containing an album by a band named The Lords. At her apartment, she and Whitey listen to the record, which is a series of string and woodwind instruments playing several notes, then repeating itself. Heidi has a vision of women who worship Satan, at an unspecified time in the past, ritually birthing a baby then damning the child. The vision stops once Whitey turns the record off.
The next day, Heidi interviews Francis Matthias (Bruce Davison), who has written a book about the Salem witch trials. The station then plays the Lords’ record, which causes all of the women in Salem (other than Heidi) to enter a trance. After the show is over, Matthias tells his wife (María Conchita Alonso) that the band’s name, The Lords, bothers him. That night, Heidi’s landlord, Lacy (Judy Geeson), insists that Heidi split a bottle of wine with her and her sisters, Sonny (Dee Wallace) and Megan (Patricia Quinn). Megan, a palm reader, tells Heidi she’s fated to succumb to her dark sexual desires: “the only reason you exist”. Disturbed, Heidi leaves the party. Later, Heidi notices her dog is acting strangely. She enters the supposedly vacant apartment 5 and experiences visions of a demon and a nude witch which commands she “bleed us a king”. Heidi wakes up in bed and assumes the events in apartment 5 were a vivid nightmare.
Troubled, Heidi visits a church and falls asleep, dreaming that she is sexually assaulted by the priest present. Heidi flees the church but is faced with a ghostly entity who tells her that he has been waiting for her. Meanwhile, Matthias researches the Lords, and discovers some music in a book. After asking his wife to play the notes on their piano, confirms it’s the same music heard on the record. Matthias tracks down the author, who tells him that in the seventeenth century a Rev. Hawthorne (Andrew Prine) accused a coven of Satan worshippers of creating the music to control the women of Salem. As a result, Hawthorne had the women executed, but not before their leader, Margaret Morgan (Meg Foster), put a curse on both the Salem women and Hawthorne’s descendants, calling his bloodline “the vessel by which the devil’s child would inherit the earth”. Further research shows Heidi is a descendant of Rev. Hawthorne.
Heidi’s radio station announces they will be giving away tickets to the upcoming Lords of Salem concert, and the record is played again, which causes Heidi to have more strange visions that disturb her. Distraught, she spends the night at Whitey’s home, but experiences visions before waking up in her own apartment. Heidi begins using drugs again. While under the influence of drugs, Lacy, Sonny, and Megan take Heidi to apartment 5. Inside, there appears to be a huge opera house with a demon seated on a throne at the top of a staircase. She approaches him as he screams and embraces her with tentacle-like appendages, but later she finds her way back to her bedroom.
The next day, Matthias tries to tell Heidi the truth about the Lords and her lineage. Instead, Lacy and her sisters kill him. Heidi hears his murder taking place, but does nothing. Later at the concert, Heidi joins Lacy, Sonny, Megan, and the ghosts of Margaret and her coven in a satanic ritual. The Lords’ music causes the female audience members to strip off their clothing. In the midst of surreal visions, Heidi blissfully gives birth to a strange creature which looks akin to a crawfish, atop the corpses of the naked audience members. The next day, Heidi’s station reports on a mass suicide at a rock concert, as well as the disappearance of Heidi.