On September 1, 1753, Paris sets off fireworks to celebrate the anniversary of the king's coronation. A great crowd mills along the river, Grenouille among them on the right bank. the fireworks bore him, as he finds their smell monotonous. As he prepares to leave, he catches a whisper of a delicate scent that nearly eludes him. Grenouille is in agony as his heart aches for the scent. He feels it's the key to assigning order to all the other odors, and feels sick with excitement.
This is the first time we see Grenouille experience real emotion. Notice, however, that what this scent inspires is the desire to hunt and control, to possess; in short, for Grenouille to exert dominance over this scent, whatever it is. Despite previous chapters in which the reader has been asked to feel sympathy for Grenouille, this feels sinister.
Grenouille decides the scent is coming from across the bridge and follows the scent through the crowd. He thinks that the scent has a freshness and a warmth like nothing else he's ever experienced. Grenouille feels as though the scent is drawing him in, and he continues his hunt through the empty streets.
Grenouille's inability to figure out what the scent is only adds to the drama of this scene. Combined with his belief that the scent is drawing him in, rather than him hunting it, it makes it seem as though the source of the scent is complicit, and Grenouille himself has no agency in the matter.
Grenouille turns onto the rue de Marais and the scent gets stronger and purer. Finally, after a series of courtyards, he sees a girl, 13 or 14 years old, sitting at a table, cleaning and pitting plums by candlelight. Grenouille realizes that the scent is coming from the girl and is confused, as he knows humans to smell repulsive. He consults his eyes for only a moment and returns to enjoying the smell of the girl, finding that every scent he'd mentally created up to this point is meaningless in light of this girl's scent.
This is wholly unexpected for Grenouille. Up to this point his experiences with people have been unmentionable in an olfactory sense, and he's been neglected or abused physically and emotionally. This is the first time that a person has meant anything important to him, and realizing this is a difficult thing for Grenouille.
Grenouille decides that he has to possess this scent or his life will have no meaning. He approaches the girl slowly and stops right behind her. She has red hair and very white skin. She doesn't see Grenouille, but notes a chill of fear. She turns around and comes face to face with Grenouille. In her terror, she doesn't cry or fight him as he strangles her. He doesn't notice any of her physical beauty, as he keeps his eyes closed.
Note the color of the girl's hair; this will be important later. Remember too that Grenouille's lack of personal scent is what makes him so terrifying. On an instinctual, primal level, this girl wasn't able to detect the presence of another person, according to the premise of the novel.
When the girl is dead, Grenouille tears off her dress and smells her bare skin from head to toe. When her scent finally fades, he collects himself for a bit and then blows out her candle. He begins his walk home as the crowd from the fireworks disperses. By the time the girl's body is discovered, Grenouille is already across the river.
This scene is simultaneously horrific and fascinating. Grenouille becomes more of an object than a person here, as he transitions from being a potentially sympathetic protagonist into something wholly inhuman and unemotional, adding to the novel's grotesque nature.
That night, Grenouille thinks of his closet as a palace and can't sleep for bliss. He feels as though he's been born for the first time, as now he realizes that he's a genius and must "revolutionize the odiferous world" by using his talents to become the greatest perfumer of all. Grenouille also takes time that night to inspect and arrange the scents in his memory, and over the next week he refines his system. He begins to construct an inner fortress of smell. Grenouille feels no remorse at having murdered the girl; all that matters to him is that he now possesses her scent.
Grenouille now has a goal, and he takes immediate personal steps to get there by constructing his “fortress.” This inner fortress will be important going forward, as it's where Grenouille's ideal world plays out. It allows him to exercise his misanthropy and hatred of the people around him, and revel in the scent world he takes so much pleasure in.