Tansy

Lore & Background

In the pharmacological tradition of the empire, tansy is catalogued alongside other bitter Asteraceae herbs as a 'heat-clearing' agent. A properly prepared decoction—two or three pinches of dried flower-heads steeped briefly—draws down fever, settles a queasy stomach, and has long been recommended for women's periodic ailments. Court physicians in the inner palace keep a small quantity on hand, and its sharp, almost medicinal bitterness is something a regular patient would expect in a cup of tea.

The danger lies in the thujone-rich essential oil concentrated in the glandular trichomes of the leaves. When the plant is macerated in alcohol for an extended period, or when a large quantity of fresh foliage is forced into a small volume of liquid, the thujone load rises sharply. The compound is a GABA-A receptor antagonist: at moderate levels it produces a warm, disorienting euphoria and mild visual distortion; at higher levels it triggers intractable nausea, photophobia, and vivid hallucinations; beyond that, generalized tonic-clonic seizures and, in extreme overdoses, respiratory collapse.

The insidious quality that makes tansy a favored tool of the unscrupulous is that early symptoms—mild dizziness, a strange metallic-bitter aftertaste, slightly blurred vision—resemble a common summer heatstroke or a mild food indisposition, buying the perpetrator hours before the picture becomes unmistakable.

Maomao's approach to a suspected tansy case is methodical: she first confirms the bitter-camphor odor on the victim's breath and vomitus, then checks for the characteristic yellowish discoloration on any cloth the victim touched, and finally assesses the neurological timeline. Her treatment is largely supportive—inducing emesis if the ingestion is recent, administering a binding agent to limit further thujone absorption, and monitoring seizure activity while the volatile compound metabolizes. She has noted, in her private observations, that the herb's duality makes it a poor choice for a careless poisoner but a brilliant one for someone who understands dosing precisely, because the margin between a therapeutic cup and a lethal one is only a matter of leaf count and steeping time.

Reader's Guide

In-world name: Ku-ai (苦艾), the 'bitter mugwort' of the imperial pharmacopoeia; sometimes loosely grouped with the broader 'ai' (艾) family in common parlance.

Botanical origin: A perennial herb of the Asteraceae (daisy) family, Tanacetum vulgare. Grows in damp meadows, ditch banks, and shaded garden corners. The usable parts are the finely dissected leaves and the small yellow-green flower-heads harvested in mid-summer before the seeds set.

Preparation & concealment: As a medicine, two to three pinches of dried flower-heads are steeped briefly in hot water (under two minutes) to limit thujone extraction, yielding a bitter, faintly golden infusion. As a poison, the fresh leaves are macerated in rice wine or distilled spirits for twelve to twenty-four hours, concentrating the volatile oil into a palatable, strongly flavored tincture that can be slipped into tea, broth, or a medicinal decoction without raising suspicion. The residual camphor-bitterness is masked by ginger or honey. Yellow staining on linen or cup rims is the telltale residue.

Symptom timeline: Onset (15–45 min): metallic-bitter aftertaste, mild dizziness, slight visual blurring, warm facial flushing—easily mistaken for heatstroke or a mild gastric upset. Peak (1–4 hr): pronounced nausea and vomiting, photophobia, vivid visual and auditory hallucinations (commonly described as seeing one's reflection move independently or hearing one's own voice from another room), confusion, and in severe cases, generalized tonic-clonic seizures. Terminal phase (4–12 hr, extreme overdose only): repeated seizure activity, respiratory depression, coma. Recovery is possible if the thujone load is below the convulsive threshold and supportive care is prompt; the hallucinatory phase typically resolves within 6–10 hours as the volatile compound is exhaled and metabolized.

Treatment Maomao devises: If ingestion is within the first hour, she induces emesis with ipecac-root tincture and administers a charcoal or clay binding agent to limit further absorption. She keeps the patient in a dark, quiet room to reduce sensory-triggered seizures, monitors breathing closely, and gives small doses of a calming chrysanthemum-and-lotus-root decoction to ease the GABA-mediated agitation without introducing additional CNS depressants. She explicitly avoids alcohol, which would accelerate thujone absorption. Recovery is judged by the return of clear, unhallucinated speech and stable pupillary response.

Recurring tool or one-off: Tansy functions as a recurring motif in the series' pharmacology rather than a single-arc weapon. Its duality—legitimate fever tonic versus dose-dependent neurotoxin—makes it a natural subject for Maomao's diagnostic reasoning across multiple cases, and it appears in her private notes as a cautionary example of how a household remedy becomes a murder weapon with a change in leaf count and steeping time.

Did You Know?

• Tansy's volatile oil leaves a distinctive yellowish stain on fabric, which is one of the first physical clues Maomao checks on a victim's clothing or bedding before relying on symptom history alone.
• Because early tansy toxicity mimics a common summer heatstroke, a poisoner who understands the herb's timeline can buy several hours of plausible deniability before the hallucinatory phase makes the true cause obvious.