The Sirens of Titan is a 1959 science-fiction novel by American author Kurt Vonnegut. In the novel, questions of free will are explored when Martians invade Earth. As in many of Vonnegut's novels, the novel uses dark humor and irony to portray humanity. The novel has not yet been adapted for other media, despite numerous attempts. This guide uses an eBook copy of the 1975 Coronet edition of the novel.

Content Warning: The source material features depictions of sexual assault.

Plot Summary

The novel is set in an unspecified future time period, sometime between the end of World War II and what is described as the Third Great Depression. Malachi Constant is the richest man in the United States. He has become rich thanks to an astonishing form of luck, which he believes is a gift from God. Using this luck, he grew his father's already sizeable fortune after inheriting the family company, Magnum Opus.

One day, Constant is invited to an estate in Rhode Island at which a man named Winston Niles Rumfoord and his dog Kazak will materialize. Like Constant, Rumfoord is a very wealthy man. He and his wife Beatrice are well-known and well-respected throughout North America. Rumfoord uses his wealth to indulge his interest in space exploration. Nine years before the materialization, he built a spaceship and piloted it through a time warp known as a “chrono-synclastic infundibulum.” The journey changed Rumfoord. He is now able to glimpse into both the past and the future. However, Rumfoord and Kazak now only exist as a long spiral stretching across the galaxy. Occasionally, Earth's orbit brings it into contact with this spiral and Rumfoord materializes on Earth for a short time, as well as on other planets.

When Constant attends the materialization at the estate, he is one of the only humans ever personally invited by Rumfoord to witness the event. However, he finds the meeting disturbing. Rumfoord's ability to see into the past and the future allows him to make predictions about Constant's life. Rumfoord says that Constant will father a child with Beatrice Rumfoord on the planet Mars. He claims that, in the future, Constant himself will travel between Mars and Mercury before returning to Earth and then travelling to Titan, one of Saturn's moons. On Titan, Rumfoord says, Constant will see a group of beautiful women. Rumfoord shows Constant a picture of these so-called Sirens of Titan as a way to show him the many temptations waiting for him there.

Constant dislikes Rumfoord’s predictions and decides that he must stop them from coming true. He throws a huge party, using all his money to entertain guests for 56 days. When the party is over and Constant sobers up, he discovers that he has bankrupted his family's business. Constant’s father, Noel, wrote a letter to be read if the business failed and left it in the hotel that he lived in. Constant therefore goes to the hotel and reads his father's letter. Once he has read the letter, two recruiters, Helmholtz and Wiley, appear. They offer Constant a position in the Martian army, which is now plotting an invasion of Earth. Keen to avoid bankruptcy and the lawsuits which will follow, Constant accepts. At the same time, the Martians also recruit Beatrice and take her to Mars. Constant and Beatrice travel to Mars, though they are not aware of each other's presence on the spaceship. Constant is told that a beautiful woman is in his room and is given the key. He enters the room and sexually assaults her, only then realizing her identity. He is overcome with regret.

When they reach their destination, the Martians erase the humans' memories. Constant must have his memory wiped numerous times because he seems resistant to the process. Constant is renamed Unk and made a private in the Martian Army. One day, he is forced to execute a soldier named Stony Stevenson. He does not realize that Stevenson is actually his best friend. Meanwhile, Beatrice gives birth to Constant's child, Chrono, and works as a teacher. Before the Martian Army invades Earth, Constant runs away to find Beatrice and Chrono. He is captured and sent with a soldier named Boaz to fight on Earth.

While travelling, Rumfoord appears to Constant and Boaz and explains that he planned the entire invasion. He describes his journey to Mars, how he planned for Constant to impregnant Beatrice, and how he wanted Chrono to be born. Constant, with his memory erased, is confused. The Martian invasion fails spectacularly, to the point where the humans are ashamed to slaughter the Martians so easily. In this moment of shame, Rumfoord introduces a new religion to Earth: the Church of God the Utterly Indifferent.

Meanwhile, the ship with Constant and Boaz is sent to Mercury. Constant and Boaz spend three years on Mercury before Constant escapes, leaving Boaz behind to care for the local creatures he discovered in the planet’s cave system. Constant returns to Earth, where Rumfoord’s religion has grown. The religion preaches that God does not care about humanity. Malachi Constant is criticized by the religion as an example of someone who mistook good luck for the blessing of God. The religion also prophesizes that Constant will return so, when he does, he is hailed as the Space Wanderer. He is taken to the Rhode Island estate.

When he materializes, Rumfoord humiliates Constant, Beatrice, and Chrono in front of a crowd of true believers. He boards them on a ship which carries them to Titan. There, Rumfoord is already waiting for them. In Rumfoord’s palace on Titan, he explains that all human history is guided by Salo, a machine which is stranded on Titan and which has directed the development of humanity. Humanity’s entire purpose is to eventually produce a replacement part for Salo’s spaceship to allow him to return home to the planet, Tralfamadore. That piece is a good luck charm belonging to Chrono. Rumfoord then dies, moving on to somewhere else in the universe. Salo, sad to see Rumfoord go, dismantles himself in grief. Constant and Beatrice live out their lives on Titan with Chrono. Eventually, Constant rebuilds Salo and, after Beatrice's death, Salo returns him to Earth. Constant sits down at a freezing cold bus stop and dies of exposure. Before he dies—thanks to Salo's brain conditioning—he imagines his friend Stony taking him to heaven, where Beatrice waits for him to arrive.