Story summary

寄生体のあらすじ

著者：アーサー・コナン・ドイル

読了8分
9 parts
音声は近日公開

A skeptical professor lets a lame stranger mesmerize him and soon cannot trust his own steps at night.

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寄生体の概要

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読書時間: 約1 h 10 min55 min fast, 1 h 25 min slow
所要時間: 16,500語
ライブラリ内の難易度: やさしいです short sentences, plain words
初版刊行年: 1894by アーサー・コナン・ドイル

Reading time at 238 words a minute (fast 300, slow 200). 古典を読むのにかかる時間 · 更新日 22 October 2026

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寄生体 in short

The Parasite follows a confident professor who thinks the mind is only a product of the body. A mesmerist named Miss Penclosa shows him a power that moves a person like a puppet. Gilroy, proud and curious, volunteers to study it, and the experiment slowly turns him into her subject.

What 寄生体 is about

What would it take to make a man of science believe in a power he openly laughs at? In The Parasite, Professor Austin Gilroy is a physiologist who trusts only what he can weigh, cut and see under a microscope. Then, one spring evening, he watches the young woman he loves fall into a trance at the command of a small, lame stranger.

Arthur Conan Doyle, who trained as a doctor, wrote this short novel in the 1890s. Gilroy tells it himself in diary entries from late March into early May, so you read his thoughts day by day. You get a tight story about a rational man and a will stronger than his own, and a plain question. How much of what you do is really yours?

対象読者. You will love this if you enjoy Victorian ghost stories and chilling psychological tales, or if you like narrators who write their fears down as they happen.

The story in 9 parts

Key idea 1 · free to read
A man of science proud of his certainty
The story opens on the twenty-fourth of March in Professor Gilroy's laboratory. He writes his diary in a brisk, self-satisfied voice. He holds a prized university chair, and he calls himself a materialist. In his view the brain makes the mind as the liver makes bile.
His friend Professor Wilson thinks otherwise. Wilson gives his life to psychology and chases evidence of the mind's hidden powers. Gilroy thinks half his subjects are frauds and the other half hysterical. Until someone shows him something he can measure, he will keep to the body.
The diary also shows what Gilroy will not say aloud. He is nervous, dreamy and sensitive, a boy who once walked in his sleep. He keeps the journal partly to steady himself. He is engaged to Agatha Marden, and he has a respected name and a quiet life. Doyle builds all of this with care, because every piece will be taken apart.
A man who trusts only what he can measure has no defence against a danger he refuses to name.
2
An evening that begins with a trance
On the evening of the twenty-fourth, Gilroy goes to Wilson's house with deep reluctance.
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3
A note, a visit, and a broken engagement
As Gilroy says good night, Miss Penclosa slips a folded paper into his hand.
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4
The skeptic becomes the willing subject
Gilroy's conversion is quick and eager.
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5
Unwelcome feelings and a pull he cannot explain
On the fourth of April, Gilroy writes a confession he would tell no one.
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6
A locked door, a night walk, and a cruel scene
Gilroy plans a simple defence.
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7
Her revenge ruins his lectures and his name
Soon after, Miss Penclosa visits Gilroy in his study.
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8
What the story asks about will and science
The Parasite is, first, a story about free will.
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9
How a diary tells the horror
Doyle tells the whole story in Gilroy's journal, and the choice shapes everything.
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Read all 9 key ideas now

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Characters, plot and themes

Main characters

Austin Gilroy A young physiology professor who trusts only fact and proof, and who tells the story in his diary while his control over himself fades.
Helen Penclosa A small, lame woman from Trinidad with strange gray-green eyes, who has a rare power to command other minds and wants Gilroy's love.
Agatha Marden Gilroy's fiancée, a bright and gentle young woman whom he wants to marry and protect from harm.
Professor Wilson A tireless psychologist who hunts for proof of the mind's hidden powers and sees every person as a case worth recording.
Charles Sadler Gilroy's neighbor and a young anatomy demonstrator, who knows Miss Penclosa's methods and tries to warn him.
Professor Pratt-Haldane A solid, practical colleague who treats Gilroy's troubles as overwork and prescribes rest and sedatives.
Mrs. Marden Agatha's mother, who wants the marriage settled properly and worries about Gilroy's failing health.

How it ends (spoiler)

Gilroy wakes in Agatha's boudoir with a bottle of strong acid on his knees and fears that he was sent there to harm her. Agatha has been delayed by a visitor, so no harm is done. He asks whether she will always love and trust him, then runs to Miss Penclosa's house intending to end the threat. A maid at the door tells him that Miss Penclosa died that afternoon at half past three.

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『寄生体』についての質問

What is The Parasite by Arthur Conan Doyle about?

It follows Professor Austin Gilroy, a skeptical scientist who agrees to be mesmerized by Miss Penclosa. As her hold on his actions grows, he fights to keep his career, his engagement and his sense of self.

Who is the parasite in The Parasite?

The parasite is Miss Penclosa, who describes how she can send her will into another person's body. Gilroy uses the word for her, comparing her to a hermit crab that takes over a shell.

Is The Parasite a ghost story or a science story?

It sits between the two. Gilroy insists that mesmerism is a natural force that science does not yet understand, while the mood is that of a Victorian horror tale about unseen power over the mind.

When was The Parasite written and is it a true story?

Doyle wrote it in the 1890s as fiction. It draws on the real public interest of that time in mesmerism, hypnotism and psychical research, but the characters and events are invented.

Is The Parasite easy to read?

Yes, in the sense that it is a short novel told in dated diary entries, with a clear voice, quick scenes and plain events, so the story is easy to follow from one day to the next.

この版を引用します

Doyle, Arthur Conan. The Parasite. Library of Alexandria, 2026, libraryofalexandria.com/products/the-parasite.

Doyle, A. C. (2026). The parasite. Library of Alexandria. https://libraryofalexandria.com/products/the-parasite (Original work published 1894)

Doyle, Arthur Conan. The Parasite. Library of Alexandria, 2026. https://libraryofalexandria.com/products/the-parasite.

@book{doyle2026parasite,
  author = {Doyle, Arthur Conan},
  title = {The Parasite},
  publisher = {Library of Alexandria},
  year = {2026},
  url = {https://libraryofalexandria.com/products/the-parasite},
  note = {First published 1894}
}