While at school, the unnamed narrator and two fellow university students, Pam Stuyvesant and Lucas Medlar, take part in a magical ritual under the guidance of Yaxley. Somehow they touch another realm, the Pleroma, and find themselves unable to escape its effects throughout the rest of their lives. Each one brings back a familiar. For Pam it is a ghostly white couple forever engaged in sexual embrace, for Lucas it is a monkeylike creature who constantly disrupts his life and surroundings, and for the narrator, apparently more blessed, it is the sight and smell of roses.
Twenty years later, Pam and Lucas have married, then divorced, but are unable to get by without each other. During their marriage, Lucas invented the autobiography of Michael Ashman to entertain Pam, and it has grown into an elaborate construct about Ashman’s quest for the Coeur, an enchanted medieval land now vanished from the world but that reflects, in some curious way, the Pleroma. The narrator keeps in touch with Pam and Lucas only sporadically, building his own career and marriage in London, but he cannot quite get away from Yaxley, who involves him in further dispiriting and unsuccessful magical rituals. One of these is a sordid incident in which the narrator finds himself bringing a teenage girl to London for a ritual that will involve her having sex with her own estranged father. Almost inevitably the scheme fails, but even his self-disgust will not allow the narrator to break free of Yaxley until the mage himself dies.
The three are brought together again by Pam’s final illness, during which the narrator finds out for the first time about their familiars and about the Coeur. When Pam dies, a final vision suggests that the Coeur was more than fiction and that Pam and Lucas had in their way been more blessed by the Pleroma than the narrator, who returns to an ordinary life in which his wife is killed and his child grows apart from him.