A plague has struck the island of St. Hubert—an island colonized by the British in the Southern West Indies. The governor of the island is Sir Robert Fairlamb, who, prior to the spread of the plague, had fired the rat catcher of the island upon Kellett the Red Leg's suggestion. George William Vertigan, Kellet's nemesis, is upset complains of this decision because he claims that the rats carry diseases. The Surgeon General, Inchcape Jones, however, claims that the island is free of disease, and thus the rat-catcher is unnecessary.
Later, when a ship arrives in the town of Blackwater in St. Hubert, carrying the plague, the disease is spread by rats. Dr. Stokes, the parish medical officer of Swithin Parish warns Inchcape about the plague and its probable spread. Inchcape, however, does not head the warnings of Stokes. Soon there are people dead, including George William Vertigan. Still, there is no action on behalf of the Surgeon General for quarantine or any such remedy. Stokes takes matters into his own hands and contacts Dr. Gottlieb, the director of the McGurk Institute about the plague on the island with a plea, explaining that the plague was about to "flare up and consume" the West Indies.
There are rumors about Martin having a cure for Plague, and yet Gottlieb does not move to action when he hears about the outbreak on the island of St. Hubert. It is not until later, when Ross McGurk talks to him and tells that were they to help the island it could bring the institute world fame, that Gottlieb calls Martin into his office. It is not known why Gottlieb decides to act, whether it is out of kindness or because of McGurk's comments relating to fame. Nevertheless, Gottlieb asks Martin to go to the island and conduct an experiment with his phage in order to deduce its real value. Martin is catapulted into instant notoriety—people interview and everyone is all of sudden interested in him. Sondelius is to go with Martin, though his opinions of what is to be done with the phage differ from Martin's. Sondelius believes that the phage should be given to all. Martin believes that the phage should be given to half, so that he may monitor and take notes and come to a conclusion about the phage. In short, Martin wants to run an experiment, and Sondelius wants to cure everyone. In fact, when it comes time to leave for the island, Sondelius refuses to take his dose of the phage, until everyone is allowed to receive it.
The Board of Trustees agrees to Martin's terms although, Inchcape Jones has not yet admitted to there being a breakout of the plague. Leora insists on joining Martin, and so Gottlieb gives her the title of "Secretary and Technical Assistant to the McGurk Plague and Bacteriophage Commission to the Lesser Antilles." Before Martin leaves, Gottlieb tells Martin to make sure not to let his heart get the best of him and to go ahead with the experiment no matter what; Terry tells him to remember to take careful notes.
The day before the McGurk Commission (Martin, Sondelius, and Leora) sets out for St. Hubert, Dr. Inchcape Jones finally issues a quarantine on the island. Once on the ship, Martin becomes seasick, while Sondelius gallivants and meets Miss Gwilliam, a rich New Jersey spinster who is going to the West Indies to "preserve primitive art." Sondelius and Miss Gwilliam do not, to say the least, get along.
Throughout this section, there is constant attention paid to the amount of love and affection that Leora has for Martin and vice versa.
Once near to the island, the plan is to anchor the boat far in the harbor and have a launch take those who are destined for the island onto the island. Nothing is to be brought onto the ship from the island, except mail, which shall be disinfected.
Martin tells Leora, before they get onto the launch, that she can still turn back; Leora refuses. Dr. Stokes, welcomes the commission on the launch and sails them to the island's shore. He tells them on the way about some of the conditions on the island and the death of the port doctor. A silent woman in black also joins the commission on the launch and disappears once they arrive onto the island.
Once on the island, Dr. Inchcape greets them and apologizes for their lack of hospitality. Sondelius does all the talking to the authorities. Later, it is discovered that Ira Hinkley is on the island when Ira, Martin's old medical school colleague, pays Martin a visit. Ira goes on and on about the "wickedness of the natives" and so on. Martin dislikes him immediately.
The group is placed in a lodge (Penrith Lodge) that is safe and rat-proof. While in the lodge, Martin is visited by a black doctor named Oliver Marchand, who talks with Martin about the phage and its fundamental nature. After their talk, Martin has to re-evaluate his prejudices, for, in arrogance, he had thought that the "Negro" was less inferior.
Sondelius becomes a kind of "dictator" and takes charge immediately, having done this kind of work before and immediately takes to thoroughly killing the rats on the island.
There is much that needs to be looked at carefully in this section regarding symbolism and character analysis.
First there is the symbolism of the woman in black. When Martin, Leora, and Sondelius step onto the launch that is headed for the island, a woman in black steps on with them. No one knows who she is, and she disappears after they come ashore. She represents death. What is most important about this is that the woman makes certain a terrible foreboding that exists throughout the chapter. For instance, the love between Leora and Martin is visited and re-visited throughout these chapters, to the extent that we feel as if something might happen to Leora or to Martin. The fact that Martin continuously regrets having brought Leora and that he feels fear heightens the sense of foreboding in us, which culminates in the image of the lady in black. Furthermore, we see that the Commission is bringing with it both life and death. In his suitcase, Martin carries the phage, which is life, but the woman in black who arrives with the group is juxtaposed against this. It is the fact that the woman arrives with the group that is most foreboding because it is already evident that death exists on the island. However, when a symbol of death arrives with Leora, Martin, and Sondelius, it points to the fact that something may happen to them.
As far as character, one of the most important characters in these sections is Sondelius. Sondelius takes charge immediately and knows exactly what to do and what to say when and to whom. We must ask ourselves about Sondelius's intentions. It becomes obvious that Sondelius loves thrill, adventure, and even the power that comes with heroic actions. It is also apparent that he has a bit of the martyr in him, when, for instance, he refuses to take the phage until it is dispensed to all of the people on the island. However, it is of utmost importance that we realize that these are not Sondelius's only motivations, because Sondelius is one of the few characters in the novel that, although raucous, has a good heart. After he fumigates warehouses and feels sorry for the straggling men who went unnoticed, and he stays behind to die with the rats—the tramps, vagabonds, and stowaways that die with the fumigation. Furthermore, Sondelius is efficient and chapter 33 ends with the following words: It happened that he [Sondelius] was, without Martin or Gottlieb ever understanding it, the most brilliant as well as the least pompous and therefore the least appreciated warrior against epidemics that the world has known." There are a few things to be said about this last sentence: first there is the element of satire in the wording of "warrior" that was seen previously in Sondelius—a kind of critique of his overzealous spirit. Nevertheless, it is also sincere and, in many ways, is almost like a eulogy, which is praiseful and yet somewhat foreboding as well.