On an early night in the canyon, a river guide sits by the fire and tells the guests about a white trumpet-shaped bloom that opens after dark. It grows in the wash. It is beautiful. Processed correctly, it will take a person’s capacity to refuse and leave everything else intact, so that the victim is awake, pleasant, cooperative and later unable to say why. There are folk names for it in several languages, and none of them are affectionate. My Sister Is Going to Kill Me by Nina Simon puts that story in front of the reader early, and then lets it sit there for two hundred pages.
Some pages later, the same guests are being pitched a luxury product derived from that plant, marketed as freedom from worry and freedom from regret. Nobody at the fire connects the two, because nobody is supposed to. My Sister Is Going to Kill Me by Nina Simon spends four hundred pages closing the gap between a campfire story and a press release, and the gap turns out to be the whole crime.
The Comedy in My Sister Is Going to Kill Me by Nina Simon Works as a Delivery System
None of this reads as grim, which is the trick. The surface of the novel is extremely good company: an influencer live-streaming her skincare routine at river level, a river guide who spent a full year in the canyon wearing a sheepskin garment he processed himself, paddles improvised from stripped camping chairs and a cast-iron skillet, a party of exhausted people arguing about whether a dead woman’s luggage counts as evidence or as sunscreen.
Simon writes this ensemble the way a good host works a difficult dinner party. Everyone gets a line. The jokes arrive at the exact moment the tension needs venting, and then the vent closes again. Readers who came to her through her debut will recognise the register immediately, and will also notice that the temperature underneath it has dropped several degrees.
Two Investigations Running in Opposite Directions
The Chisholm sisters are the reason the book works. Liv is a State Department professional whose whole occupation is the detection of deception, and who has responded to a childhood spent around a con artist by refusing, as a matter of principle, to lie about anything at all. Mandy teaches high school art, embellishes reflexively, and has never met a room she could not improve with a small fiction.
The structural gamble of My Sister Is Going to Kill Me by Nina Simon comes from separating them for a long central stretch, forcing each to work in the other’s idiom. Liv, who cannot lie, has to invent a story to keep a frightened group functional, and discovers she is unnervingly good at it. Mandy, who cannot stop lying, has to say something true to her father and watch it land like a slap. Both attempts are clumsy. Both change the person making them.
The payoff is quiet and rather lovely: when the two halves of the case finally meet, one sister has the who and the how, the other has the why, and the novel does not pretend either could have finished the job alone.
The Industry Satire Is the Sharpest Thing Here
My Sister Is Going to Kill Me by Nina Simon finds its sharpest register in the economics of the wellness trade. A founder who makes decisions on instinct and expects her siblings to reconcile the ledgers. A dermatologist paid in equity to stop asking about a fatal accident in a focus group. A brother who explains, in the flattest possible voice, that the line between attraction and addiction is difficult to measure, and offers lip balm as his example.
The novel understands that the real vulnerability of a beauty company is not its formula but its byproducts and its paperwork. The active compound in the plant at the centre of the story is a real one, used in ordinary medicine as a prescription drug for motion sickness and, in concentrated form, notorious for something else entirely. Regulators have been explicit for years that health and wellness marketing claims must be substantiated, and Simon builds her motive squarely on the gap between what a brand promises and what a supply chain actually produces. It is the most interesting idea in the book, and it is treated with no sentimentality whatsoever.
Where My Sister Is Going to Kill Me by Nina Simon Overreaches
The cast outgrows the page count. Between the founding family, the former employee, the marketing lead, the influencer and her chaperone, and four guides, several suspects receive one memorable detail and are then held in reserve until the plot needs them.
The villain’s competence arrives retroactively. A great deal of expertise is attributed off the page and after the fact, and it asks for more credulity than the carefully fair clue placement elsewhere has earned.
The final explanation is talked rather than dramatised. The motive is genuinely chilling, and it is largely delivered in two heat-stunned conversations over a contract folder.
None of these sink the book. They keep an excellent mystery from being a great one.
The Canyon Will Not Cooperate
The setting deserves its own paragraph, because My Sister Is Going to Kill Me by Nina Simon refuses to use the canyon as a set. A closed-circle mystery normally depends on the circle staying closed. This one keeps rupturing. Boats are taken, groups are severed, half the party goes downstream while the other half stays with a body and no radio, and the same geography that seals everyone in keeps reshuffling who is sealed in with whom. The investigation has to run without a coroner, an evidence bag, or the option of asking anyone to stay put.
The result is that every question costs something. Liv cannot interview a suspect without giving up river miles. Mandy cannot keep a group calm without lying to it. The wilderness is not atmosphere here; it is the constraint that makes the detective work interesting.
Where to Go After This
Mother-Daughter Murder Night is the obvious next stop, and the sharper comparison: three generations of women, a coastal slough, and the same conviction that family friction beats forensics. Death on the Island by Eliza Reid serves the pure locked-location craving, with a remote setting and a guest list nobody can leave. Readers who want the corporate rot without the whitewater should try The Cloisters by Katy Hays or, for something colder and funnier about people monetising other people’s feelings, Yellowface by R. F. Kuang.
What My Sister Is Going to Kill Me by Nina Simon Really Argues
Strip out the rafting and this is a novel about consent, and about what it costs to have your judgement quietly removed while you remain polite about it. The plant does it chemically. The brand does it commercially. The father has been doing it to his daughters, affectionately, for thirty years, and one of them built a career on detecting it while the other built a personality on performing it.
My Sister Is Going to Kill Me by Nina Simon ends on a line of five words that turns the entire relationship inside out, and it is the right ending, because it insists that the two sisters were never opposites. They were the same instrument, tuned differently, waiting for a river loud enough to make them play together.