During his fourth week at the Lido, von Aschenbach notices something is amiss. The number of guests at the hotel is falling rapidly, and there are no other German guests. The barber mentions offhand that he is staying on despite "the disease," but then refuses to define the disease. Von Aschenbach goes downtown immediately, and identifies the smell of germicide in the air. The city is plastered with posters warning against eating seafood. He asks a shopkeeper about the smell, and the man dismisses it, saying that it is a precautionary matter mainly of the police's concern.
At the hotel, von Aschenbach looks for news, but cannot find anything but vague warnings and reassurances. He feels that Venice is hushing up a dirty secret akin to his own secret of loving Tadzio, and is also concerned that Tadzio might leave to flee the epidemic. He follows the boy more regularly, even to a mass in Venice. He tails the Polish family around the city, follows them in a gondola, and is upset when he thinks they have noticed him. He justifies his obsession with the idea that it was the fashion in Ancient Greece for older men to love younger boys.
Von Aschenbach continues to search through German-language newspapers, which report an epidemic and criticize the Italian government for trying to hush it up, but also report retractions making the scale of the problem hard to measure. Von Aschenbach confronts the manager of the hotel about the plans to disinfect Venice, and considers the manager a hypocrite when he claims germicide is only a precaution.
Von Aschenbach attends a street singer performance in the front garden of the hotel. Although the music is sentimental and of poor quality, von Aschenbach enjoys it, as passion tends to debase artistic sensibilities. Tadzio is there, but guarded by his governess and mother, who have begun to notice von Aschenbach's attentions. When the singer comes around to collect money, von Aschenbach asks him why Venice is being disinfected, and the singer denies there is a disease. The singers perform a final song that has the audience laughing, but von Aschenbach remains somber. When he notices that Tadzio has also remained somber, von Aschenbach wonders despairingly if the boy is reacting to his own facial expressions. Von Aschenbach sits up at his table long after Tadzio and the other guests go to bed.
The next day, von Aschenbach goes to a British travel agency, where a travel agent finally tells him the truth. He says that a fatal Indian cholera had first moved east to China, west to Afghanistan and as far north as Moscow. It moved along trade routes, showing up in some Mediterranean cities including Palermo and Naples. In mid-May it hit Venice, but the cases were kept secret by the government, for fear of disturbing tourism. The travel agent urges von Aschenbach to leave Venice immediately.
Von Aschenbach imagines warning Tadzio's mother, although he has never spoken to her, but decides to collude in the secret and say nothing. He has a bad dream that night, filled with fear and desire as he watches a savage crowd dance and howl to the music of a flute, and joins them in worship of what he terms the "strangergod." He wakes up unnerved, and sees that most guests have fled the hotel. However, the Polish family remains, and von Aschenbach imagines everyone else might die so he can be left with Tadzio.
Von Aschenbach wishes to please Tadzio, and therefore begins to add colorful touches to his clothing. Next, he goes to the barber, who dyes his hair black, curls it, plucks his eyebrows, and adds makeup (rouge) to his face, to make him appear younger. Von Aschenbach is pleased, but confused. A storm wind begins to blow and the air turns humid. Von Aschenbach feels feverish.
He trails Tadzio around Venice, and although the boy looks back and realizes what von Aschenbach is doing, he does not tell his family. When he loses track of the Polish family, von Aschenbach buys and eats some overripe strawberries and finds himself in the same square in which he had decided to leave Venice a few weeks earlier. He sinks down on the steps of a well in the middle of the square, and dreamily talks aloud to Phaedrus, a cipher for Tadzio. He argues that although artists try to renounce the abyss of moral degeneracy, they are still drawn to it. He concludes that he will go and "Phaedrus" will remain, and when "Phaedrus" no longer sees him, then he will go too.
A few days later, von Aschenbach leaves his hotel to go for a walk and suffers from dizzy spells. He sees a large amount of luggage in the hotel lobby, and asks who is leaving, although he already seems to know the answer. He learns that the Polish family is leaving after lunch. He sees Tadzio playing with his friends, who are stronger than he is, but less beautiful. Jasiu defeats his friend in a wrestling match, driving his head hard into the sand. Von Aschenbach is about to rescue him when the other boys stop Jasiu. Tadzio walks away, and looks back at von Aschenbach, who sets out to follow him. Minutes later, people rush to the aid of von Aschenbach, who has slumped in his chair. That same day, the world learns of the famous writer's death.
In the final chapter of a tragedy, inevitability catches up with the protagonist. The gap of dramatic irony between the reader and the protagonist is closed somewhat, as von Aschenbach accepts certain facts he had been denying. Von Aschenbach begins to be more honest with himself about his false Platonic ideal, and begins to pursue Tadzio as an idol. Moreover, he becomes the rouge wearing older man in search of youth that he so despised on the boat trip to Venice, when he changes his appearance to please Tadzio.
The representation of Venice, which has been uneasy throughout the novella, takes a decided turn for the more sordid. Von Aschenbach describes it as a labyrinth, the presence of the water making it a mysterious and somewhat sick place. Of course, the city is literally sickened by the onset of the cholera epidemic, and von Aschenbach's earlier description of it as a "tourist trap" rings true. If the Venetian authorities were honest about the medical state of the city, a quarantine would be imposed and von Aschenbach would not be able to leave anyway. Ultimately, Venice traps von Aschenbach, becoming the city where the famous man buys overripe strawberries, contracts cholera, and dies.
The leitmotif of the sinister stranger appears for a final time in this chapter. The street singer who performs at von Aschenbach's hotel is reminiscent of the stranger in the graveyard and the gondolier. The singer also wears a specific hat, has large Adam's apple, and reddish hair. This death's head or Grim Reaper figure has become increasingly ominous throughout the chapters, as he moves physically closer to von Aschenbach and is available for more extensive conversation. The street singer is accompanied by the smell of carbolic acid, a germicide that foreshadows von Aschenbach's death.
The British travel agent's realistic description of the spread of the disease pins down the vague sense that fate is out to get von Aschenbach. The description of the Ganges Delta resonates exactly with von Aschenbach's original dream in Chapter One of a dense and dangerous jungle. He is destined not only to die in Venice, but to die of this exotic, tropical disease. By reading backwards, this original dream finally takes its proper significance.
The ending is slightly anti-climactic. In three short sentences, Thomas Mann brings us out of the claustrophobic world of the hotel in Venice, and widens the scope to the entire world. Von Aschenbach's personal history is finished, and the secret of his moral degeneration dies with him. Strangely enough, his public history remains unchanged, despite his experiences in Venice. His artistic reputation remains unharmed, and the world mourns the loss of a great author, and no more.