Robin’s sapphire engagement ring symbolizes Robin’s commitment to her fiancé, Matthew. It is a tangible sign of their long-term relationship and intention to build a future together. However, even at the novel’s beginning, Robin notes that the ring has “become a little loose on her finger” (6). Her observation that it no longer fits snugly hints at Robin’s uncertainty over whether marriage to Matthew is the right fit for her. Growing tensions in the couple’s relationship, playing into The Dynamics of Partnership Under Stress, are evident from their frequent arguments, invariably prompted by Matthew’s disapproval of Robin’s work as a private investigator, an aspect of her life she considers central to her identity. As the novel unfolds, the engagement ring becomes a recurring emblem of Robin’s internal struggle between the conventional life Matthew represents and authenticity. The ring’s presence on her finger increasingly symbolizes containment rather than love.

Following Matthew’s admission of infidelity, Robin takes the engagement ring off, leaving it “on a bookshelf loaded with [Matthew’s] old accountancy textbooks” (209). The gesture symbolizes her rejection of Matthew and the conformist life that his career in accountancy represents. Remaining untouched on the shelf for weeks, the ring conveys Robin’s indecision as she fails to reconcile with Matthew, but lacks the courage to cancel their forthcoming wedding. Ultimately, her decision to put the ring back on is prompted by the romantic atmosphere of the televised royal wedding and Robin’s nostalgic recollection of Matthew presenting her with “the winking sapphire” (211) when he proposed.

Robin’s engagement ring also possesses a shifting significance for Strike. He recalls that, in the early days of their relationship, “The sapphire on Robin’s third finger had been a bonus […]: a safeguard and a full stop” (389). The visible sign of her commitment to another man prevented him from perceiving her as anything other than a colleague and friend. When Robin removes her ring in Career of Evil, Strike becomes more honest with himself about his attraction to her. The reappearance of “the sapphire sparkling coolly from her finger again” (381) requires a further emotional adjustment and his attempts to reassert professional distance in their relationship.

Music is a recurring motif that intensifies the mood of Career of Evil and contributes to its themes. The novel’s title is taken from a Blue Öyster Cult song, conveying the book’s focus on three suspects who have made a lifelong commitment to evil. Furthermore, the beginning of each chapter references a song title or lyrics from the same hard rock band. Blue Öyster Cult is best known for the hit single “(Don’t Fear) The Reaper.” In Galbraith’s novel, allusions to their songs—which often reference death, the occult, and science fiction—create a macabre and sinister tone.

The motif of music is introduced early in the plot when the killer sends a severed leg to Robin, accompanied by a note quoting “Mistress of the Salmon Salt” (Quicklime Girl) by Blue Öyster Cult. The song’s lyrics link the crime to Strike’s childhood, underscoring The Past’s Impact on the Present: Strike immediately recognizes the lyrics from his mother, Leda’s, fixation with Blue Öyster Cult and its frontman Eric Bloom. Readers learn that the obsession inspired his middle name, “Blue,” and that Leda had the title of her favorite song, “Mistress of the Salmon Salt,” tattooed on her body. Leda’s relationship with music and musicians is embodied in Strike’s recollections of his abusive stepfather, Jeff Whitaker. The lyrics act as emotional triggers, forcing Strike to confront unresolved feelings about his upbringing.

The killer’s narrative perspective illustrates his own obsession with Blue Öyster Cult. Galbraith highlights how the surreal and opaque lyrics of the band’s songs are open to many interpretations. Consequently, the killer is convinced the band articulates his own misogynistic and warped worldview: “The Cult (as he privately called them) seemed to understand. They got it” (446). Through the killer’s response, the author explores how music can reinforce an individual’s darker inclinations. This idea is echoed in Strike’s memories of Whittaker’s testimony in court after Leda’s death. Alluding to “Mistress of the Salmon Salt,” he claimed that Leda “wanted to die. She was the quicklime girl” (73). The assertion highlights how death is often glamorized in certain forms of art.