Kaiser is one of Geo’s two best friends in high school and becomes a love interest in the dramatic present. In this role, Kaiser serves as a foil, his selfless love for Geo contrasting with Calvin’s possessive treatment of her and thus contributing to a thematic look at Manipulation and Control in Abusive Relationships. Because nearly half of the story is told from a limited third-person point of view focused on Kaiser, he can also be considered the deuteragonist, or the second most important character. His main function in the story, however, lies in his relationship with Geo and its influence on her. As a detective, his conflict with the unknown killer seems important to the plot, but its relevance fizzles out as Geo learns the killer’s identity, faces him, and eliminates him without meaningful involvement from Kaiser. His character isn’t crucial, then, to solving the mystery. Instead, his role is to give Geo the love and forgiveness she needs to overcome her own conflicts.

Hillier uses both direct and indirect characterization to depict Kaiser. The former includes Geo’s interpretation of her friend, while the latter includes his choice of women and his actions toward Geo. Geo says that there has “always been kindness at Kaiser’s core” and describes him as her moral compass (13). Kaiser is more critical of himself, believing that his greatest weakness has always been falling for unavailable women, with his unrequited love for Geo in their youth being the prime example. Details such as Kaiser’s affair with his married partner, Kim, support Kaiser’s words while lending complexity to his character; he tries to do the right thing but does not always do so. The affair also underscores how this attraction to unavailable women has affected his life. Indeed, it has led to Kaiser’s primary internal conflict in the dramatic present—his sense that he’s no longer capable of really loving anyone due to his experience loving Geo.

After Angela disappears, Kaiser is motivated by a need for closure in the form of knowledge and justice. Learning what happened 14 years later allows him to tell Geo that he doesn’t hate her anymore and that he can finally let it go now that he knows the truth. He achieves justice for Angela when he arrests Calvin, but Calvin’s escape reignites the force motivating Kaiser to act. His epiphany about the real reason Geo missed half of their junior year in high school—her pregnancy—helps him see the latest murders in a new light. It also marks a turning point in his character arc, as it helps him see Geo differently and moves him toward her and another chance at real love.

Calvin is a convicted serial killer known as the “Sweetbay Strangler” and one of the book’s two antagonists. His good looks and charm are significant aspects of his characterization because they are what enable him to captivate and manipulate young women. Angela describes Calvin in his early twenties as “beautiful,” with a face like Jared Leto’s and a “vibe” like Kurt Cobain’s. During his trial, when he is 35, Geo notes that he still looks like a movie star. 

Calvin’s initial characterization is largely shaped by Geo’s testimony during his trial, in which his “obsessive and controlling nature” becomes apparent as she describes the physical and verbal abuse she endured (6). Through flashbacks that depict his and Geo’s romance, Calvin’s character thus contributes to a thematic portrayal of manipulation and control in abusive relationships. Geo’s testimony also contributes significantly to Calvin’s public reputation, although the revelation that it was Geo who proposed dismembering Angela—and that he covered for Geo during his trial—somewhat complicates this picture. 

Though elucidating Calvin’s psychology is not the point of the story, other details likewise give depth to his character and complicate the mystery. His statement that people like him “should not exist” implies some level of moral awareness (245), if not actual remorse. Another notable character trait is Calvin’s belief that he loves Geo. The narrative tone makes it clear that his abusive actions belie real love, but he seems to lack insight into this fact. Ultimately, however, Calvin’s primary motivation is straightforward and self-interested: to avoid negative consequences for his actions. Murdering Angela is an impulsive crime, not a premeditated one, but he doesn’t display remorse afterward. Instead, his only concern is covering it up so that he isn’t implicated. It’s unclear whether his future murders occur because he realizes that he enjoys killing or merely because he sees it as an effective way to get away with rape, but they cement his status as a villainous figure.

Dominic is Jar of Hearts’s second antagonist. He is conceived when Calvin rapes Geo and then given up for adoption. In the dramatic present, Dominic is a killer, responsible for the deaths of Sweetbay’s four latest murder victims. The investigation into his murders and the threat he poses to Geo and the Sweetbay community are at the heart of the text’s primary external conflict. 

Dominic’s connection to Geo is a plot twist that isn’t revealed until late in the narrative arc, so his characterization is limited. His foster parent does offer a telling detail when Kaiser questions her about Dominic’s use of superhero names in his letters to Geo: “‘That’s something he’d do,’ Ursula says with a laugh. ‘He always wished he was someone else’” (88). This fact hints at Dominic’s painful childhood and the motivation for his crimes. Dominic’s experiences with neglectful adoptive parents, abuse, abandonment, and the foster system are indirect outcomes of Geo’s choice to give him up for adoption, a choice she made because she was raped. Those experiences and their influence on Dominic’s actions contribute to the text’s thematic representation of the enduring trauma of violent crimes.

In Geo’s climactic confrontation with Dominic, his character provides her with the opportunity to express love, something that trauma and grief have long made impossible for her. His inability to recognize love develops the novel’s message about love in practice: “He doesn’t know what love looks like. He doesn’t know what love feels like. Love—healthy love, the kind that doesn’t hurt or bruise or take away someone’s sense of self-worth—is like anything else that’s important in life. It has to be taught” (298). Geo sees Dominic’s ignorance as forgivable for this reason—a conclusion that helps her see her 16-year-old self as forgivable too. Dominic also provides Geo with the opportunity to atone. Loving him despite what he’s done atones for the love she couldn’t give him during his lifetime, while killing him, and thereby preventing more murders, atones for the deaths that her past secrecy and inaction permitted.

Angela is Geo and Kaiser’s best friend in high school and Calvin’s first murder victim. As the cheerleading squad’s captain, a star on the volleyball team, and an honor student, Angela has everything going for her, making her death at age 16 especially tragic. She’s also portrayed as extremely pretty and popular, traits that emphasize jealousy as a primary source of conflict in the story. Other girls are always jealous of Angela, even Geo, which helps explain Calvin’s hold over Geo. In turn, Angela becomes jealous of the attention that Calvin pays to Geo, leading her to flirt with him and fight with Geo. 

Though Angela isn’t a fully developed character, she does display some depth, which is relevant to how Geo views their friendship and honors her memory. When she’s mad at Geo, she makes a hurtful comment about her weight in front of the cheer squad “to be nasty, and to embarrass her in front of the other girls” (143). In contrast, Angela’s demeanor with Geo after they make up shows that she can be very caring and loyal. Ultimately, Geo’s remorse for her role in Angela’s death and subsequent cover-up haunts her, causing emotional dysfunction that illustrates the psychological weight of guilt and secrets. Geo’s grief over the loss of her friend, as well as tormenting memories of witnessing Angela’s gruesome death, embodies the enduring trauma of violent crimes.

Ella is an incarcerated woman who protects Geo as part of their business partnership. Ella previously ran a security team for her husband, a notorious drug lord, and was convicted of murdering two of his rivals. In prison, she runs her own drug operation, for which Geo provides financial services including money laundering. Ella’s character fleshes out the nature of prison as a setting, inviting questions about how much suffering is enough for someone to be forgiven, either by society or by themselves. Ella’s character also develops Geo’s external conflict with the other women in prison, who pose a potentially violent threat, creating tension and stakes.

Cat is Geo’s best friend in prison and the first real friend she’s had since Angela died. Cat, who was sentenced to 15 years in prison for killing someone while driving drunk, is portrayed as someone who made some big mistakes but is a good person at heart. Her character serves as a parallel and model for Geo’s, helping her to recognize goodness in herself despite the destructive mistakes she’s made. Similarly, Cat’s cancer provides Geo with an opportunity to regain some measure of control by helping Cat through treatment in a way she couldn’t help her mother. Cat’s main functions in the story are to help Geo survive the emotional burdens of prison, to exacerbate Geo’s grief and sense of loss, and to enable Geo to express love.

Walt is Geo’s father and her model for love and forgiveness. Their relationship in Geo’s teenage years shows how selfless Geo is before she is traumatized by Calvin’s abuse and Angela’s murder. Her efforts to shield him from the harm of her criminal record and notoriety show that she still has that selflessness inside her even if she can no longer see it. Walt’s support of Geo in the wake of Angela’s disappearance, during Geo’s pregnancy, and after Geo’s release from prison reminds Geo that unconditional love and forgiveness are possible.

Claire and Sasha are two of Dominic’s murder victims. Kaiser’s investigation reveals that they both had short-lived relationships with Calvin after he escaped from prison—neither realized that he was the Sweetbay Strangler—that resulted in pregnancy. One was a law school student and an intern at a prestigious law firm. The other grew up in a trailer park and had severe drug addictions. Despite their differences, both young women physically resembled Geo—part of the circumstantial evidence that leads Kaiser to think that Calvin killed them but actually a testament to Calvin’s enduring (though problematic) love of Geo. Like Angela, both women were dismembered before burial, which complicates the link to Calvin (who did not regularly do this to the women he killed) and foreshadows the revelation that it was Geo who dismembered Angela.

Henry and Emily are Calvin’s biological children and Dominic’s murder victims. Kaiser’s investigation reveals that Henry, a 22-month-old, and Emily, a four-year-old, were conceived during short-lived romances that Calvin had with their mothers and then given up for adoption. Dominic uses lipstick to draw hearts on their bodies and the words “SEE ME.” It’s a message for Geo, whom he blames for choosing his adoptive parents poorly and for all his subsequent suffering. As child victims, Henry and Emily illustrate the depth of Dominic’s rage and trauma: He tells Geo that he killed them because they shouldn’t get to have good lives and good parents when he didn’t. Their deaths also create high stakes for Geo and Kaiser’s conflict with the killer, adding tension and suspense.