Themes Blood on Her Tongue Johanna van Veen

Sisterhood and Codependency: The Unbreakable (and Toxic) Bond in Blood on Her Tongue

Thematic Claim

In Blood on Her Tongue, Johanna van Veen explores the dark side of sisterly devotion, arguing that a twin bond built on unequal dependence can mutate into a justification for murder, self-abnegation, and the erasure of self. Lucy Goedhart’s identity is so thoroughly fused with her twin Sarah’s that she will sacrifice her own morality, safety, and future to protect whatever wears Sarah’s face—even when she knows it is a parasite that has consumed her sister from within. The novel does not celebrate this loyalty; instead, it forces the reader to question when love becomes an excuse for complicity and how easily compassion can serve self-destruction.

Tracing the Bond Across the Plot

Arrival at Zwartwater: The Submissive Twin Answers the Call

From the first chapter, Lucy defines herself as a “weaker copy” of Sarah. When she receives Sarah’s panicked letter about the bog body, she rushes to Zwartwater without hesitation. The author’s note confirms that the book is in part a study of toxic codependent relationships, and Lucy’s immediate journey sets that theme in motion. In Chapter 2, Lucy finds Sarah emaciated, paranoid, and violent—yet Lucy’s first instinct is not to flee but to comfort. She promises Sarah she will never send her to an asylum, a vow that seals her eventual complicity. Lucy’s childhood memory of a worm torn in half foreshadows her own sense of being incomplete without her twin; she would rather serve a monstrous sister than have no sister at all.

Feeding the Parasite: Lucy’s Moral Slippery Slope

The middle of the novel shows Lucy’s moral calculus in action. In Chapter 18, Not-Sarah confesses she is a parasite who has consumed Sarah’s consciousness and now wears her rotting body. Lucy’s internal debate is raw: she wonders if a person is the sum of their memories, and if Not-Sarah has those, perhaps she can still be a sister. This philosophical rationalization leads to practical aid. In a later scene, Lucy cuts her own arm to feed Not-Sarah, and when that is not enough, she helps Katje do the same. The act of self-harm becomes a ritual of love, but the clear-headed reader sees it as codependency’s logical endpoint. Lucy admits she would rather have a parasite-sister than no sister, a declaration that strips away any pretense of healthy attachment.

Murder in the Name of Sisterhood

The climax in Chapter 26 crystallizes the theme. Lucy kills Michael to prevent him from harming Not-Sarah, then kills Arthur when he tries to manipulate her. These murders are not framed as heroic; they are desperate, violent acts born of a bond that has erased all other ethical considerations. Not-Sarah gleefully drinks Michael’s blood, and the two sisters plan to escape with Katje, staging an elopement that allows them to vanish. The newspaper article that closes the chapter reports them as missing, speculating that the bog claimed them—a fitting metaphor for how the sisters have been swallowed by their own toxic union. Lucy’s final actions prove that codependency, left unchecked, can destroy everything outside its orbit.

Character and Symbol Connections

Lucy and Sarah / Not-Sarah

Lucy is the submissive twin, her identity almost entirely dependent on her sister. As van Veen explains in the author conversation, Lucy’s “shadow-like” existence stems from her role as the weaker half. Sarah (and later Not-Sarah) is dominant, but the parasite twist adds a layer: Lucy’s love is so unconditional that she continues to serve an entity that killed her original sister. Not-Sarah exploits this devotion, begging for help and reminding Lucy of their twin bond whenever she hesitates. The scene where Not-Sarah whispers “You know I’d do the same for you” reveals how the relationship weaponizes mutual sacrifice.

Katje as a Dark Mirror

Katje, the maid who is also in love with Not-Sarah, parallels Lucy’s devotion. She lets Not-Sarah feed from her even before Lucy knows the truth, weakening herself to the point of fainting. When Lucy confronts her, Katje insists she would kill for Not-Sarah. Together, the two women form a feeding chain: they sustain the parasite because they cannot imagine life without its host. Katje’s presence underscores that codependency is not limited to blood sisters—it can infect any intimate bond.

Key Symbols

  • Blood and Feeding: The act of giving blood becomes a sacrament of sisterhood. Lucy’s self-cutting mirrors the bite marks on Katje’s wrist, and the shared bowl of blood in Chapter 18 is almost eucharistic. Yet the novel uses this imagery to show how love can be vampiric, draining the giver.
  • The Bog Body: Marianne, the original corpse, is the catalyst for Sarah’s transformation. The bog represents preservation and decay; just as the bog preserves bodies, the sisters’ bond preserves a relationship that should have rotted away. Lucy’s promise to never let Sarah be “taken away” echoes the bog’s refusal to let go.
  • The Silver Pen / Eye Gouging: The pen Michael gives Lucy becomes a weapon when Sarah uses it to blind herself. The gouging is both self-harm and a desperate attempt to expel the parasite. Lucy later associates the pen with her own complicity—she dropped it, and Sarah found it. The twinned nib of a replacement pen (splitting, doubling every stroke) mirrors the twin identity that cannot be separated.
  • The Posy Ring: Though less central, the posy ring Sarah wears might symbolize a binding promise. Van Veen uses it to hint at the permanence of vows—Lucy’s vow to protect Sarah at all costs becomes a ring she cannot remove.

Complexity and Contradiction

The novel refuses to present Lucy’s sacrifice as admirable. Van Veen’s conversation directly addresses the “mercy kill” trope, asking when killing becomes about placating one’s own fear rather than showing mercy. Lucy’s murders are not mercy to Michael or Arthur; they are self-serving acts to preserve the illusion of sisterhood. Furthermore, the author destabilizes the idea that Not-Sarah is purely evil. Not-Sarah retains Sarah’s memories and emotions, and she loves Lucy in her way—but that love is also predatory. The ambiguity forces readers to confront the discomfort of rooting for Lucy while recognizing her choices are destructive. The epilogue-style newspaper clipping leaves the three women missing, not triumphant, suggesting that codependency offers no happy ending.

Study Questions

1. How does Lucy’s identity as the “submissive twin” drive her willingness to help Not-Sarah?
Lucy defines herself entirely by her relationship to Sarah. When she believes Sarah is gone, her sense of self shatters. Rather than grieve, she clings to the entity that looks and acts like Sarah, because having a monster-sister is preferable to being no sister at all. Her self-worth is so entangled with Sarah’s existence that she abandons her own moral boundaries to keep that connection alive.

2. In what ways does the feeding ritual symbolize the codependency between Lucy and Not-Sarah?
The shared bowl of blood in Chapter 18 transforms nourishment into a bond of complicity. Lucy cuts her own arm and Katje cuts her wrist; they literally give parts of themselves to sustain the parasite. This symbolic act shows that codependency requires constant sacrifice—the sisters are bound by blood in a literal sense, and the ritual reinforces their mutual dependence. Lucy’s later reflection that she would rather feed the parasite than lose her sister reveals how feeding becomes a substitute for genuine intimacy.

3. Why does Lucy kill Michael and Arthur? Is her action justified within the story’s moral framework?
Lucy kills Michael to prevent him from harming Not-Sarah, and Arthur because he tries to manipulate her. The novel does not present these killings as morally right; they are desperate acts driven by fear and love. Van Veen’s conversation about “mercy kills” suggests that such actions often serve the killer’s own need to control the situation rather than true mercy. Within the story’s framework, Lucy’s justification is personal, not universal—the reader is left to judge whether her love excuses her violence.

4. How does the character of Katje mirror Lucy’s codependency?
Katje is also in love with Not-Sarah and willingly feeds her, even fainting from blood loss. She tells Lucy she would kill for Not-Sarah with no hesitation. Katje has no blood relation, yet her devotion is just as intense as Lucy’s. This parallel shows that codependency is not limited to siblings; any intimate relationship can become parasitic when one partner sacrifices their own well-being to serve the other. Katje’s weaker physical state highlights the cost of such devotion.

5. What does the ambiguous ending (the three women missing) suggest about the future of Lucy’s bond with Not-Sarah?
The newspaper clipping reports the three women missing, with speculation that the bog claimed them. This open ending implies that Lucy, Not-Sarah, and Katje have escaped society’s judgment, but they have not achieved a healthy life. They are still bound together, presumably continuing to feed the parasite. Van Veen imagines them on a European tour, balancing safety and curiosity, but the threat of discovery or decay remains. The ending suggests that codependency offers no cure—only a continued, nomadic existence built on lies and blood.