He does and they find the mangled remains of his brother in the family factory, his head and arm crushed under a hydraulic machine press.
Then one day, Henri inquires how long a housefly's life span is and says he saw the fly his mother wants to catch, which has a white head.
Realizing that this might somehow hold a clue to the murder, François confronts her with the news that Henri spotted a strange fly, and Hélène becomes extremely agitated.
Hélène's manuscript reveals that at first André encountered several flukes, including an experiment in which he transmitted an ashtray that reintegrated in the receiver pod with the words "Made in Japan" on the back written backwards.
Unbeknownst to him, a housefly had entered the transmitter pod with him, and when he emerged from the receiver, his head and arm had been switched with that of the insect.
Now realizing that he has been transformed beyond all hope, André destroys the pods and all of the work in his lab and devises a way to commit suicide while at the same time hiding from the world what he had become.
But just as the story ends, François tells Charas that earlier that day he killed a fly and buried it at his brother's graveside.
The Jungian analyst Marie-Louise von Franz discusses the story in her lectures on "The Inferior Function", an aspect of the theory of psychological types.
After summarising the plot (adding "I have spared you most of the disgusting and perverse details in the story, which are expounded with great gusto"), she comments:There one sees how inferior intuition takes shape in a sensation production.
One sees that he would represent collective common sense – the verdict finally adopted by the writer, who admits that all this is just madness.
If the writer had established the continuity of his inferior function, and had freed it from his extroverted sensation, then a really pure and clean story would have come out.