The disaster wasn't an external one, the narrator says, but rather one that took place in the deepest part of Grenouille's dream fantasies. One night he lies on his sofa in his purple fortress, asleep after drinking a huge amount, including two bottles of the scent of the girl from the rue de Marais. While Grenouille's sleep is usually dreamless, on this night he experiences wisps of dreams floating past. The wisps begin to grow thicker and finally, Grenouille feels as though he's standing in rising fog. The fog wraps around Grenouille and he can't catch his breath. The fog is Grenouille's own body odor, and with horror, Grenouille realizes he can't smell it.
Finally, in a dream, Grenouille realizes what others have realized since his infancy and finds that he doesn't smell. The knowledge of this is terrifying and threatens to kill him, an apt and symbolic representation of what's to come. Notably as well, it's his continued desire for the scent of the girl from the rue de Marais that gets him drunk enough to experience dreams like this.
Grenouille begins to scream, and the scream wakes him. He thinks that the fog would've suffocated him and he would have died, and he feels very afraid. Grenouille resolves to change his life so that he won't have to experience such a frightening dream again. He creeps out of his cave and squats in the sunshine, still shaken by his dream, thinking that it's a good thing the outside world still exists. After a few hours Grenouille has calmed down and returned to normal.
For the first time, Grenouille's inner world is a dangerous place rather than someplace safe and wonderful, which leads him to a greater appreciation of the outside world.
Grenouille smells his fingers and smells nothing but the spring air. He tries the crook of his elbow, his genitals, armpits, his feet, and smells nothing. He rationalizes that he's dulled to his own scent and if he could wean himself from his scent for a while, he'd then be able to smell it. He strips off his clothes, leaves them in a pile, and climbs to the top of the mountain. He stands like a diver about to jump and allows the wind to cleanse him of his smell for several hours.
This entire sequence, while deadly serious for Grenouille, is comic for the reader as we might imagine Grenouille attempting to smell himself at the top of the mountain. While the novel is a very serious one, it's these moments that remind the reader that the story is also ridiculous and absurd, despite its underlying horror.
When evening comes, a very sunburnt Grenouille returns to his pile of clothes. He performs the sniffing test he learned from Baldini and still smells nothing aside from the natural world he's inhabited for the last seven years. He becomes alarmed and afraid. This fear isn't the same fear he experienced in the dream; rather, it's the fear that he knows nothing about himself.
Finally we learn what Grenouille’s fear is truly about: it's about coming of age and not knowing who or what he truly is. This is a quest for self-knowledge more than anything else, which situates the novel as a whole as a kind of twisted bildungsroman.
Deciding he must know if he has a scent, Grenouille crawls back into his cave, fighting the fear from his dream and the fear of knowing nothing about himself. At the back of the cave, he squats for a long time and smells nothing but the cave. Grenouille nods to himself, exits the cave, pulls on his clothes, and begins to head south.