Grandfather's death (dramatic irony)
Captain Cook's death is an example of dramatic irony because it undermines the reader's expectations of the story. Because of the specter of yellow fever hovering over the plot, it seems most likely that if anyone is going to die, it will be due to the epidemic. Captain Cook is also elderly and in frail health, so it could be possible for him to die due to an age-related health concern. Given all these more probable causes of death, it is ironic that he ends up dying due to injuries sustained in a violent confrontation. This irony keeps the plot interesting by surprising the reader, and also reveals that there is no real way to predict where danger will come from.
Colette's elopement (dramatic irony)
Late in the novel, Mattie learns that Colette Ogilvie had secretly eloped with her French tutor. This news is ironic because earlier in the story, Colette had been very snobby and rude about Mattie's social position. Colette had implied that Mattie would not be good enough to marry into the Ogilvie family and that she disapproved of people marrying outside of their social classes. However, all along, Colette was ironically involved with a man of a much lower social rank. The irony is compounded when it is also revealed that Colette's sister Jeannine is also in love with the same man, revealing that both sisters are hypocrites.
The spread of the fever (dramatic irony)
In the first few chapters of the novel, many of the residents of Philadelphia refuse to believe that the outbreak of disease is actually yellow fever. They cling to the belief that nothing is seriously wrong and that the situation will resolve itself. Readers, however, know that the disease is very grave and is only going to get worse. This dramatic irony creates tension because readers can see that many people are making dangerous decisions and delaying taking actions that might actually decrease the death toll. In times of crisis, people often want to cling to normalcy for as long as possible, and this tendency can create danger.
Mrs. Cook going to the farm (dramatic irony)
A pattern of situational irony is perpetuated by the confusion of the Cook family members trying to track each other down. Mrs. Cook goes to the Ludington farm to see her daughter and father-in-law, but then they're not there, so she goes in pursuit of them, which leads to Captain Cook being unable to find her when he reaches out to her at the farm. All of the confusing back-and-forth is ironic because it subverts the reader's expectations of the family staying together and working together during the epidemic. The irony of the confusion and inability to locate each other reflects the overall chaos of the epidemic, as well as how it unsettles all aspects of life.
