At a strange Satanic ceremony, a young woman is forced to stare into a looking glass. She sees the image of a demonlike creature, sending her into a frenzy and causing her to repeatedly strike her head on a stone pillar.
The master of the Satanic cult wants to try again, and this time he chooses another girl, Allison. Allison flees the building and evades the members of the cult by hiding behind a bush.
Meanwhile, at an auction, Laura Stephens, accompanied by her fellow antique dealer Michael Roberts, bids on some items in a box, once owned by a late Earl. Going outside and looking inside the box, she spots a mirror exactly like the one used in the Satanic ritual. Another dealer, Simon andrews, looks at the mirror and starts to offer her successively higher bids for the object. Getting suspicious, Michael offers to get the mirror appraised for Laura.
While driving, Michael looks into the mirror lying on the passenger seat. It clouds over and Michael goes into a strange trance. At the same time Allison, who is still trying to evade capture, also goes into a trance. Eventually, she runs in front of Michael's car. She asks for Michael's help, and she gets into the car.
Michael takes Allison to his house. She spots the mirror and says that she can feel an enormous power emanating from it. She tells Michael that it is a scrying glass, perhaps made by the late astrologer John Dee. She tells him that the Chorozon Society would pay a lot of money for it. While Michael is not looking, Allison disappears with the glass.
The next day Michael arrives at Laura's antique shop and tells her what has happened. He explains that he will track Allison down and get the scrying glass back.
He then goes to Simon Andrews antique shop and manages to find out that the Chorozon Society is the client that wants the glass.
Michael does some research on the subject of Chorozon, and he finds that he is the guardian of the abyss. Many people have tried and failed to summon Chorozon up. He discovers that in order to make Chorozon flesh, the human subject must be born on the solstice, be in possession of the scrying glass and go to the place of invocation eagerly.
The master of the Chorozon Society, Charles Randolph, again tries to contact Allison through the scrying glass and is successful. Frightened, she takes the glass back to Michael.
Charles Randolph performs a ceremony in which he brings two voodoo dolls together over a scrying glass. Simultaneously, Michael and Allison are brought together in a clinch. That night, Michael and Allison sleep together.
Later, Charles Randolph performs another ceremony using a sacrificial chicken and a dagger. He picks up a dagger with the female doll and stabs at the male doll. At the same time Allison attempts to stab Michael while he is lying in bed. Just in time, he leaps out of bed and breaks Allison from her trance.
The next morning Randolph is at Mike's door. He warns Mike about Allison, telling him that she is dangerous, disturbed and paranoid. He then tries to hypnotise Mike and get him to offer him red wine, bread and salt. Allison comes running into the room and flings the tray across the room telling Mike that you should never offer a black magician these things in your own home. Randolph tells them that Allison is the chosen one and then leaves.
Mike takes Allison to Laura's shop and asks for her to look after Allison while he sorts things out. Mike arrives back to see Allison and Simon driving off as Laura stumbles out of the shop with blood dripping from her head where she was hit with a vase by Allison.
Simon takes Allison back to the society for the ritual. Mike gets the address of the society from Simon's assistant and when he arrives there he finds Allison lying on a bed holding the scrying glass. He takes the scrying glass from her. She is pleased to see him, but she rings a bell to inform the society. Randolph and Simon come into the room and Allison thanks Mike for coming as she was to be the chosen one had he not arrived. Allison confirms to Randolph that Mike satisfies the conditions of sacrifice.
Mike is strapped to a table. Randolph chants and then Simon raises the dagger and stabs Mike in the chest. Lightning strikes and wind howls through the room. The scrying glass cracks and the wind subsides. Chorozon is now where Mike was. Chorozon's face fades to reveal Mike's face. Mike removes the knife from his chest and breaks free from the straps. He tells his servants they have done well and orders them to the floor. Allison is beckoned to his side.