Cat’s Cradle is told retrospectively by its narrator, John, who also calls himself Jonah. From the present-day, which is just after the novel’s cataclysmic ending, John explains that he had once set out to write a book about the day the atomic bomb was dropped on Hiroshima. Specifically, he wanted to write an account of what important Americans were doing on the day. He also lets the reader know that, back then, he was a Christian; now, he is a Bokononist, a follower of a religion based on the small Caribbean island of San Lorenzo.
John begins his retrospective story. In this, he seeks to contact the children of Dr. Felix Hoenikker—Frank, Angela, and Newt—in order to find out more about the scientist (in the novel, Dr. Hoenikker is one of the “fathers” of the atomic bomb). John speaks to Newt by letter. The youngest of the siblings, Newt doesn’t remember much about that fateful day and describes his father as a brilliantly minded but emotionally stunted human being. He recalls how, on that day, his father had tried to show him a cat’s cradle with string but had ended up only upsetting Newt. Newt gives John an address for Angela, and explains that nobody knows the location of the third sibling, Frank. John also learns that Newt, a dwarf, has a brief relationship with a woman who claims to be Ukrainian dancer—Zinka—who has since left America with the help of the Russian embassy.
Roughly a year later, John takes a writing job in Ilium, New York, which happens to be where the Hoenikkers used to live, and where Dr. Hoenikker used to work—at the Research Laboratory of the General Forge and Foundry Company. John meets with locals who knew the Hoenikkers, and they generally portray the children as outcasts and Dr. Hoenikker as a clever but unfeeling individual only interested in science.
John visits the lab and is shown around by Dr. Hoenikker’s old supervisor, Dr. Asa Breed, who describes the lab as a rare place where scientists are allowed to conduct “pure research.” Dr. Breed takes offence at John’s questions, which seem to him to imply “that scientists are heartless, conscienceless … indifferent to the fate of the rest of the human race.” During this conversation, John learns that Dr. Hoenikker was once asked by the U.S. military to find a solution to “mud.” The scientist came up with an idea for a substance called ice-nine, a “seed crystal” that can make a water molecule freeze at room temperature and in turn “teach” that state to its neighboring molecules. John correctly figures out that such a substance would be highly dangerous, potentially resulting in the freezing of the world’s entire water supply. John interjects from the present-day to confirm that, contrary to Dr. Breed’s assertions, ice-nine does exist, and that each of the Hoenikker children has a portion having divided up their father’s after he died on one Christmas Eve.
John takes a writing assignment that requires him to visit San Lorenzo. Reading through a promotional magazine about the place, John learns that Frank is a government minister on the island. John also sees a picture of the beautiful Mona Aamons Monzano, the adopted daughter of the country’s aging dictator, ‘Papa’ Monzano. John reads about the checkered history of San Lorenzo, which has been ruled by various countries over the centuries despite being a relatively barren environment.
While on the plane to San Lorenzo, John meets the new American ambassador for the nation, Horlick Minton, and his wife, Claire. He also meets H. Lowe Crosby, who is a bicycle manufacturer hoping to start a factory on San Lorenzo, and his patriotic wife, Hazel. Incredibly, Angela and Newt are also onboard; they are travelling to be guests at Frank’s wedding, which John learns is to Mona. The Mintons are reading a book about San Lorenzo, from which John learns that Bokonon was born Lionel Boyd Johnson, studied at London School of Economics and ended up on San Lorenzo through a series of chance events (mostly involving ships being sunk). He learns that Bokonon and his partner, U.S. Army deserter General McCabe, planned to start a utopia on San Lorenzo. Realizing they couldn’t adequately provide for its inhabitants, Bokonon invented his religion—named after the San Lorenzian way of pronouncing his real name—to bring them comfort, meaning, and purpose. He had McCabe outlaw the religion in order to make life more exciting.
The plane lands, and there is a ceremony prepared for the arrival of the new ambassador. During this, however, ‘Papa’ Monzano is taken ill, ending the occasion abruptly. With the Crosbys, John goes to his hotel, which is owned by Philip Castle (who wrote the book the Mintons were reading). The Crosbys soon go to stay elsewhere after Philip insults them. John learns that Philip grew up in the island—his father, Julian, runs its only hospital—and was tutored alongside Mona by Bokonon. At the hotel, John walks in on two people in the Bokononist act of “boko-maru,” in which they rub their soles together in order to “mingle” their souls.
Frank urgently summons John to his house. When John arrives, Frank isn’t actually there yet. Frank spends some time with Angela, Newt, and Julian Castle. Angela explains that she believes that her father didn’t get the credit he deserves. Newt paints a picture comprised of black scrawls, saying that it is a “cat’s cradle.” Julian, judging the painting to symbolize the meaninglessness of life, throws it into the waterfall below.
Before Frank arrives, soldiers come to the house to protect “the next president.” Soon after, there is a power cut. Later on, John reads about the Bokononist creation story, which Bokonon himself calls “foma”: “a pack of lies.” When the power comes back during the night, John, Angela, and Newt all run out of their bedrooms in a panic, disturbed by the noise. John has grabbed his passport and wallet, while the Hoenikker siblings have with them, unbeknownst to John, their vials of ice-nine.
When Frank eventually arrives, he begs John to become the new president of San Lorenzo once ‘Papa’ dies—an event which is imminent. Frank feels he isn’t suited to the public responsibility, and explains that the role comes with good money and the prospect of marrying Mona. This latter fact sways John, who agrees to become president despite realizing the absurdity of doing so. He conducts boko-maru with Mona, though almost loses her by trying to order her not to have other “loves”; this contravenes her way of life, she explains, causing John to immediately adopt her Bokononist religion.
Frank and John go to see ‘Papa’ at his castle to get his blessing for John’s presidency. John plans to announce his role publicly during the commemorative ceremony for the “One Hundred Martyrs to Democracy,” one hundred young San Lorenzians who died on their way to assist America after the Pearl Harbor attack. ‘Papa’ is attended to by Dr. Schlichter von Koenigswald, who was Nazi doctor at Auschwitz and is trying now to save people’s lives to redress the balance. ‘Papa’ makes John promise to capture Bokonon, because science, not religion, “is magic that works.” ‘Papa’ keeps asking for ice, much to Dr. Koenigswald’s bafflement. ‘Papa’ dismisses the hapless Christian minister, Dr. Vox Humana, and instructs Dr. Koenigswald to deliver the Bokononist last rites—despite what he has just said to John. Dr. Koenigswald and ‘Papa’ engage in boko-maru, while ‘Papa’ repeats Dr, Koenigswald detailing the Bokononist creation myth (which says that people are “mud” that got lucky, and should be grateful to God for their brief existence).
John goes off to write his speech. He briefly considers giving Bokonon a place in his government, but realizes the usefulness of the outlawed religion—to provide the islanders with adequate food, infrastructure and other resources would be too difficult. He heads to the ceremonial gathering by the cliffs. From the buffet, John tries a piece of albatross meat. Feeling instantly ill, he rushes to find a bathroom and bumps into Dr, Koenigswald. The doctor is in a panic and gets John to come and look at ‘Papa,’ who is frozen stiff. He explains that ‘Papa’ froze after touching a substance to his lip that he kept in his necklace. In trying to clean up, Dr. Koenigswald contaminates himself with the same substance—ice-nine—and dies instantly. John confronts the Hoenikker children about ice-nine; it transpires that each of them had exchanged the technology for their own personal gain (Frank for his place on San Lorenzo; Angela for her U.S. military husband; and Newt, accidentally, for his affair with Zinka). They try to clear up, melting the ice-nine back into water and placing Dr. Koenigswald’s body in the cupboard.
Planning to burn the two bodies later, John and the Hoenikkers return to the ceremony. At this, Minton delivers a speech about the futilities of war, imploring the crowd to think of peace instead of patriotism. Just after he throws a wreath into the sea, one of the military planes flying overhead as part of the ceremony catches fire and crashes into the cliff. A great chasm opens up on the cliff face; Minton and his wife are thrown into the water. The damage to the land destabilizes “Papa’s” castle, sending his body into the sea. The contact of the ice-nine with the water instantly freezes the sea and, presumably, the entirety of the earth’s water. Multiple tornadoes appear in the sky.
John takes shelter with Mona, emerging a few days later. They discover a mass grave in which most of the islanders have committed suicide. A note informs them that they did so on the advice of Bokonon. Mona, seeing a logic to what they have done, takes some ice-nine from the contaminated earth and puts it to her lips, dying too. John is discovered by Newt and the Crosbys.
John takes refuge with the others at Frank’s house. Hazel stitches together an American flag, hoping John will place it on San Lorenzo’s mountain summit. Frank obsesses over an ant farm—ants seem to be the only insect that has survived, and they do so by sacrificing themselves to melt ice-nine with their body heat so that other ants can drink the water. One day, John takes Newt for a drive so that the latter can “forage” for paint. As he drives, he passes Bokonon and stops to talk to him. Bokonon explains that he is trying to come up with an ending for the Bokononist scriptures. When asked what he’s got so far, Bokonon shrugs and passes John a piece of paper. This reads: “If I were a younger man, I would write a history of human stupidity”; continuing that he would take ice nine and “make a statue of myself, lying on my back, grinning horribly, and thumbing my nose at You Know Who.”
