The narrator of Kurt Vonnegut’s novel Cat’s Cradle invites his readers to call him Jonah, although his parents called him John. He explains that he used to be preparing a book about what “important Americans” did on the day that the atomic bomb was dropped on Hiroshima, Japan. The book was originally intended to be factual, but he has since learned the “bittersweet lies of Bokonon” and has adopted Bokononism as his religion. The title of his original book was to be “The Day the World Ended.”

The first part of Cat’s Cradle takes part in Illium, where Felix Hoenikker, now deceased, worked on developing the atomic bomb. Felix has three children that survive him. The oldest child, Angela, took care of the family after Felix’s wife died. After a difficult adolescence, the middle child, Frank, left home. Newton Hoenikker, the youngest, is a midget who has gained a measure of notoriety for his affair with a Russian midget who turned out to be a Russian spy. The narrator writes Newton, or Newt, asking for any anecdotes that he might be able to share about his father, particularly those related to the day that America dropped atomic bombs on Japan.

Newton writes back that he remembers that his father, Felix, was playing with string on the day that the bomb was dropped and that Felix also made a cat’s cradle. Felix asked whether Newt saw the cat and the cradle. Normally, Felix Hoenikker had no use for rules and games that others made up. When he received the Nobel Prize, Hoenikker explained that he

never stopped dawdling like an eight-year-old....Anything can make me stop and look and wonder, and sometimes learn.

Newton shares that his father actually asked him to play cat’s cradle with him, but his father’s cigar smoke smelled like the “mouth of hell.” In that moment, Newton saw his father as the ugliest thing he had ever seen and ran outside.

Newt shares another story from that day. His reaction to his father’s cigar smoke and appearance, Newton’s sister Angela would later claim, was hurtful to Felix. However, Newton explains that he was not convinced of that because Felix Hoenikker was never interested in people. For example, when he ran away from his father, he went into the backyard and found his brother, Frank, who was capturing bugs and forcing them to fight in a glass jar. When Angela caught her two brothers, Frank punched her in the stomach. Although Angela tried to call upon her father for help, when Felix looked out the window and saw his children crying, he remained disinterested and returned to his study.

The narrator later interviews Dr. Asa Breed, who was Felix Hoenikker’s supervisor at the General Forge and Founder Company. Breed explains that his team had always done “pure research.” However, when the narrator asks him questions that “implied that the creators of the atomic bomb had been criminal accessories to murder most foul,” Dr. Breed disagrees. General Forge and Founder Company offers its scientists the freedom to do “pure” research, and he explains that there is great value in knowledge. After all, “the more truth we have to work with, the richer we become.” Breed urges the narrator to explain how Felix Hoenikker had the ability to approach problems with a fresh perspective.

Take “ice-nine” for example. When ice-nine touches water, it becomes a “seed crystal” that causes the molecules to turn to a unique form of ice—ice that remains solidified while at room temperature. Although it was never produced, ice-nine was a perfect illustration of how Felix Hoenikker responded originally to conventional problems. The problem, in this case, was that mud was a great irritation for the American military. Soldiers hate to march in mud, so why not create a substance that would eliminate the mud and create a smooth solid path? The marines would be able to march much more easily. The solution, Hoenniker suggests, is ice-nine.

However, the narrator points out that ice-nine would rearrange the molecules of water to the point that all of the water in the world would become solid. Ice-nine is not a solution. Rather it is a potential problem for the entire world. There is no "purity" in this research. Instead, there are great consequences that could follow its development. Breed claims that ice-nine is only theoretical. Unfortunately, Dr. Hoenikker did invent ice-nine, and each of his three children has a chip of it.

Frank, the child that left Illium, is now actually in San Lorenzo, an island nation. The narrator soon finds himself flying to the island of San Lorenzo with Newt, Angela, and an American businessman, H. Lowe Crosby and his wife, Hazel. Along the way, they read a history of San Lorenzo that is written by Philip Castle, but they cannot know for certain whether or not its information is accurate. San Lorenzo is trying to make money from tourism, although it has a mixed history when it comes to humanitarian issues.

San Lorenzo is currently ruled by “Papa” Monzano. Before that, the state was founded by Earl McCabe and a man that has since become known as Bokonon. The two exiled the priests they found on the island and began trying to improve the country. However, when their economic and political policies failed, they turned to religion to bring the people happiness. Bokononism, however, is founded entirely on lies, as Bokonon readily admits in The Books of Bokonon. To “give the religious life of the people more zest,” Bokonon asked McCabe to outlaw Bokononism. Consequently, the religion is outlawed, Bokonon lives in hiding, and its practitioners are impaled upon a large hook, a punishment that is “invariably fatal.” Before long, McCabe found that his government relied on its opposition to Bokononism, so he continued the practice, even though everyone in San Lorenzo is a Bokononist. Papa Monzano, a Bokononist, has also outlawed Bokononism.

When the narrator arrives in San Lorenzo, he meets its ruler. He also finds Frank Hoenikker, who is a Major General in San Lorenzo. Most importantly, for the narrator, he sees Mona, Monzano’s adopted daughter, for the first time and falls in love with her beauty. Monzano only has time to welcome his American visitors to the island before he collapses in pain. He has been battling cancer, so, knowing that he will die soon, he appoints Frank as his successor. Inexplicably, before he can take over the country, Frank approaches the narrator and suggests that he become president in Frank’s stead. The only catch is that he will have to marry Mona. The narrator agrees to become president of San Lorenzo.

However, things do not go as he plans. Mona is a Bokononist and she explains that she loves the narrator, but no more than she loves everyone else. After all, Bokononism, the religion of lies, teaches its followers to love everyone equally. She is quite happy to engage in “boku-maru” with the narrator, which requires two people to lie on their back and touch the soles of their feet against each other. When the narrator asks Mona to engage in boku-maru with him only, she balks because she must love everyone equally. It seems that the narrator’s rule is off to a bad start and it will only get worse.

Papa Monzano’s last instructions to the narrator are to kill Bokonon on the hook. Before he dies, he ensures that he will receive the last rites of the Bokononists. Although the narrator thinks that impaling dissidents on a hook is awful, he does not change any policy in San Lorenzo. He does instruct Frank to arrange for electricity for the island, but each time that he tells Frank what to do, the Hoenniker child replies “you’re the boss.” The narrator realizes that by becoming the president, he has

freed Frank to do what he wanted to do more than anything else, to do what his father had done: to receive honors and creature comforts while escaping human responsibilities.

What no one realized is that Frank gave his portion of ice-nine to Papa Monzano, who kept the substance in a cylinder that hangs from his neck. (It may be that he is no worse than his siblings, who managed to share the substance with the American and Russian governments.) Monzano uses the ice-nine to kill himself, by touching the substance to his fingers and then his mouth.

However, it is not until the narrator is giving his first speech as ruler of San Lorenzo that disaster strikes. The speech is to be concluded with six fighter jets firing upon the “enemies of freedom” in effigy. However, one plane malfunctions and crashes into the ruler’s palace. In the destruction that follows, Papa Monzano’s body, solidified with ice-nine crystals, enters the sea. The sea instantly solidifies. The world has ended.

The Bokononists react quickly. They commit suicide by touching ice-nine frost and then touching their mouths. Bokonon himself remains in hiding. Mona also kills herself, leaving the narrator with Newt and the Crosbys. All animals are dead, but they are perfectly preserved for anyone that takes the time to melt them and cook them. As the months pass, the narrator looks for purpose. San Lorenzo’s highest mountain, Mount McCabe, is nearby, and Hazel, who is sewing an American flag, suggests that the narrator climb the mountain and plant the flag.

However, it is only at the very end that the narrator realizes what he should do. He finds Bokonon himself, whose feet are “frosty with ice-nine.” Bokonon shares that he has come up with a final sentence for The Books of Bokonon. The novel ends as the narrator reads:

If I were a younger man, I would write a history of human stupidity; and I would climb to the top of Mount McCabe and lie down on my back with my history for a pillow; and I would take from the ground some of the blue-white poison that makes statues of men; and I would make a statue of myself, lying on my back, grinning horribly, and thumbing my nose at You Know Who.