Chapter Seventeen opens with Joe and Clarissa lying face to face in bed as if nothing is wrong, yet with silent accusations flying over their heads. Clarissa sees Joe as a manic, obsessed invader of her private space while Joe sees Clarissa as disloyal, unsupportive, and irrationally suspicious. Nonetheless, they speak cordially to each other about banal household things, conscious of the fact that a real argument might tear them apart permanently. Joe comments that they had “lost heart” and were “loveless”—although they go through the motions of being a couple, there is nothing underneath.
Joe reveals that Parry has been sending him letters three or four times a week, usually focused on his mood, the weather, the room he is in, and how sad he is to be apart from Joe. His letters often include religious references as well as subtle accusations against Joe. Joe only reads the letters for the accusations, trying to find an actual threat within them so he can report Parry to the police. Joe is convinced that Parry will eventually try to hurt him because “well over a half” of male de Clérambaults attempt violence on their obsessions, according to Joe’s research. Joe tries to lure Parry into threatening him by leaving “secret messages,” but Parry seems to only read what he wants to read—he is trapped in “love’s prison of self-reference.” Joe feels uneasy about his inability to predict Parry’s emotions. When Parry does decide to strike, it will be without warning.
Joe returns to the present, where he and Clarissa are lying in bed. He thinks about ways to get back into her heart, ways to regenerate their love, when she speaks. Clarissa tells him that they should admit that their relationship is finished. Joe ignores her and instead focuses on Jean Logan’s request. He called Toby Greene, one of the laborers, but Greene hadn’t seen anything and wasn’t helpful. Then Joe called James Gadd, the balloonist, who didn’t want to speak. Joe finally reached Joesph Lacey, the other laborer, who was cagey about whether or not there was anyone with Logan, but agreed to meet Joe.
Joe snaps back to the present as Clarissa accuses him of always thinking about Parry. She explains that she’s frightened that she’s losing him and that she doesn’t know how to get him help. She accuses him of thinking he can read his way out of this and also of having a problem while insinuating that she thinks Parry doesn’t exist. Joe refuses to recognize what Clarissa is saying, instead focusing on how Parry could turn violent. Clarissa tells Joe that she is going to go sleep in the guest children’s bedroom.
Chapter Eighteen begins on Clarissa’s birthday. Joe mentally accuses Clarissa of using her emotions as a guide instead of “information, foresight, and careful calculations.” He prepares her gift for the lunch they are going to have with her godfather, then reads through all Parry’s letters, marking significant, threatening passages. He compiles the veiled threats, wishing Clarissa, the literary critic, could help him. Threats include explaining how easy it is to kill, how he has lots of money, how he’s wanted to “more than hurt” him, and how God’s love is wrathful. While reading, Joe remarks on the lack of structure in Parry’s religion, and how Parry often equates God with the self.
Joe leaves the house with his list of threats and worries when he doesn’t see Parry on the path. He goes to the police station and makes a complaint about how his case was handled in the past. A man named Officer Linley meets with him and asks Joe about his reported harassment. He asks him many questions, but like last time, the officer fails to find anything he can do. Officer Linley suggests inviting Parry in for a cup of tea. Joe warns him that Parry will probably get violent, but Linley reminds him that they do not have enough manpower to work on suggestions of threats.
Joe heads to Clarissa’s lunch, refusing to believe that their relationship is over, having always been convinced that their “love was just the kind to endure.” He reflects on her past birthday and how he was able to focus fully on two things at once—making love to Clarissa and reading a newspaper. He had posited that he was some sort of evolutionary throw forward, which Clarissa had mocked playfully. Joe ends his reminiscence thinking about how alone he is in the fight against Parry.
In Chapter Seventeen, Joe tries to assert power over Parry with his newfound knowledge. As a rational, professionally successful man, Joe represents a classic masculine power. Parry strips Joe of that power through the control he asserts over Joe’s life. Joe attempts to regain that power by mastering Parry with knowledge, Joe’s favorite weapon. Joe imprisons Parry within a web of diagnoses and case studies, trapping the real-life threat within the confines of de Clérambault’s syndrome.
During Clarissa’s admission to Joe that she thinks that they should separate, Joe drifts in and out of focus, choosing instead to think about the balloon accident or Parry. While we as readers know that Parry is the threat that Joe thinks he is, we also become aware of how Joe is changing. Clarissa may be wrong about Parry, but she is right about Joe. Joe has changed, has become obsessed with Parry, and has started isolating himself. Much of the narration we get from Joe is introspection. He is living increasingly inside his head—just like Parry.
As Joe prepares to go to Clarissa’s lunch party, he assembles a sheet of veiled threats made by Parry. He remarks that the work “needed the skill of a literary critic like Clarissa to read between the lines” (pg. 151). Here, Joe finally recognizes his “lack” that he references while on the field. Joe’s strictly rational viewpoint doesn’t have the interpretive and ambiguous power of Clarissa’s literary viewpoint. Even though he criticizes her emotional approach to Parry, he realizes that he “lacks” the key emotional ability to read Parry’s letters for all their power.
At the end of Chapter Eighteen, Joe remarks that he cannot believe that his and Clarissa’s relationship is ending, since he always thought that their “love was just the kind to endure” (pg. 158). This references the title, while emphasizing the ambiguity of it. There are generally two definitions of "to endure": the one Joe uses to describe his relationship with Clarissa is "to last." At the beginning of the novel, Joe and Clarissa thought that their relationship would last until their deaths. Their love is simple and natural. Since Parry has come into their lives, however, their love has begun to fracture. The other definition of "to endure" is "to undergo or suffer pain, hardship, or opposition." Parry’s love for Joe is one that must be endured by Joe. Joe suffers hardship as a result of Parry’s obsession.